diff --git a/package.json b/package.json
index a85921a742..29f4823da5 100644
--- a/package.json
+++ b/package.json
@@ -30,6 +30,7 @@
   "dependencies": {
     "@atom/source-map-support": "^0.3.4",
     "@babel/core": "7.18.6",
+    "@formatjs/icu-messageformat-parser": "^2.6.1",
     "about": "file:packages/about",
     "archive-view": "file:packages/archive-view",
     "async": "3.2.4",
@@ -83,6 +84,7 @@
     "grim": "2.0.3",
     "image-view": "file:packages/image-view",
     "incompatible-packages": "file:packages/incompatible-packages",
+    "intl-messageformat": "^10.5.1",
     "jasmine-json": "~0.0",
     "jasmine-reporters": "1.1.0",
     "jasmine-tagged": "^1.1.4",
diff --git a/spec/package-manager-spec.js b/spec/package-manager-spec.js
index 6948e10eb1..aca17056a9 100644
--- a/spec/package-manager-spec.js
+++ b/spec/package-manager-spec.js
@@ -1019,7 +1019,7 @@ describe('PackageManager', () => {
 
       spyOn(pack.mainModule, 'activate').andCallThrough();
       await atom.packages.activatePackage('package-with-serialization');
-      expect(pack.mainModule.activate).toHaveBeenCalledWith({ someNumber: 77 });
+      expect(pack.mainModule.activate).toHaveBeenCalledWith({ someNumber: 77 }, { t: pack.t });
     });
 
     it('invokes ::onDidActivatePackage listeners with the activated package', async () => {
diff --git a/spec/package-spec.js b/spec/package-spec.js
index a235c4e919..899a4c9b02 100644
--- a/spec/package-spec.js
+++ b/spec/package-spec.js
@@ -18,7 +18,8 @@ describe('Package', function() {
       menuManager: atom.menu,
       contextMenuManager: atom.contextMenu,
       deserializerManager: atom.deserializers,
-      viewRegistry: atom.views
+      viewRegistry: atom.views,
+      i18n: atom.i18n
     });
 
   const buildPackage = packagePath => build(Package, packagePath);
diff --git a/src/atom-environment.js b/src/atom-environment.js
index 13682f3e76..e9c389f7c4 100644
--- a/src/atom-environment.js
+++ b/src/atom-environment.js
@@ -45,6 +45,7 @@ const TextEditor = require('./text-editor');
 const TextBuffer = require('text-buffer');
 const TextEditorRegistry = require('./text-editor-registry');
 const StartupTime = require('./startup-time');
+const I18n = require("./i18n");
 const { getReleaseChannel } = require('./get-app-details.js');
 const packagejson = require("../package.json");
 
@@ -103,6 +104,10 @@ class AtomEnvironment {
       type: 'object',
       properties: _.clone(ConfigSchema)
     });
+    /** @type {I18n} */
+    this.i18n = new I18n({
+      config: this.config
+    });
 
     /** @type {KeymapManager} */
     this.keymaps = new KeymapManager({
@@ -135,7 +140,8 @@ class AtomEnvironment {
       grammarRegistry: this.grammars,
       deserializerManager: this.deserializers,
       viewRegistry: this.views,
-      uriHandlerRegistry: this.uriHandlerRegistry
+      uriHandlerRegistry: this.uriHandlerRegistry,
+      i18n: this.i18n
     });
 
     /** @type {ThemeManager} */
@@ -266,6 +272,8 @@ class AtomEnvironment {
     });
     this.config.resetUserSettings(userSettings);
 
+    this.i18n.initialise({ resourcePath });
+
     if (projectSpecification != null && projectSpecification.config != null) {
       this.project.replace(projectSpecification);
     }
diff --git a/src/i18n.js b/src/i18n.js
new file mode 100644
index 0000000000..950730c393
--- /dev/null
+++ b/src/i18n.js
@@ -0,0 +1,415 @@
+const fs = require("fs-plus");
+const path = require("path");
+const season = require("season");
+const { default: IntlMessageFormat } = require("intl-messageformat");
+const { parse: parseToAST } = require("@formatjs/icu-messageformat-parser");
+
+/**
+ * @type {Array<{
+ *   ext: string;
+ *   parse: (s: string) => any
+ * }>}
+ */
+const supportedFileExts = [
+  {
+    ext: "cson",
+    parse: str => season.parse(str)
+  },
+  {
+    ext: "json",
+    parse: str => JSON.parse(str)
+  }
+];
+
+module.exports = class I18n {
+  /**
+   * @param {object} opts
+   * @param {import("./config")} opts.config
+   */
+  constructor({ config }) {
+    this.config = config;
+    /** @type {Array<string>} */
+    this.locales = [];
+    this.localisations = new Localisations();
+    this.resourcePath = "";
+
+    this.config.setSchema("core.languageSettings", {
+      type: "object",
+      description: "These settings currently require a full restart to take effect",
+      properties: {
+        primaryLanguage: {
+          type: "string",
+          order: 1,
+          default: "en",
+          // TODO get available languages for enum purposes
+        },
+        fallbackLanguages: {
+          type: "array",
+          order: 2,
+          description: "List of fallback languages in case something is not translated in your primary language. Note: `en` is always the last fallback language, to ensure that things at least show up.",
+          default: [],
+          items: {
+            type: "string"
+            // TODO consider array enum when enum array options are improved in settings UI?
+          }
+        }
+      }
+    });
+  }
+
+  /**
+   * @param {object} opts
+   * @param {string} opts.resourcePath
+   */
+  initialise({ resourcePath }) {
+    this.locales = [
+      this.config.get("core.languageSettings.primaryLanguage"),
+      ...this.config.get("core.languageSettings.fallbackLanguages"),
+      "en"
+    ].map(l => l.toLowerCase());
+    this.resourcePath = resourcePath;
+
+    this.localisations.initialise({ locales: this.locales }); // TODO ast cache
+
+    this._loadStringsForCore();
+  }
+
+  /**
+   * @param {Key} keystr
+   * @param {Opts} opts
+   */
+  t(keystr, opts = {}) {
+    return this.localisations.t(keystr, opts);
+  }
+
+  /**
+   * @param {string} ns
+   */
+  getT(ns) {
+    /**
+     * @param {Key} keystr
+     * @param {Opts} opts
+     */
+    return (keystr, opts = {}) => this.t(`${ns}.${keystr}`, opts);
+  }
+
+  _loadStringsForCore() {
+    this._loadStringsAt("core", path.join(this.resourcePath, "i18n"));
+  }
+
+  /**
+   * @param {object} obj
+   * @param {string} obj.pkgName
+   * @param {string} obj.pkgPath
+   */
+  loadStringsForPackage({ pkgName, pkgPath }) {
+    this._loadStringsAt(pkgName, path.join(pkgPath, "i18n"));
+  }
+
+  /**
+   * @param {string} pkgName
+   * @param {string} i18nDirPath path to the i18n dir with the files in it
+   */
+  _loadStringsAt(pkgName, i18nDirPath) {
+    if (!fs.existsSync(i18nDirPath)) return;
+
+    /** @type {Array<string>} */
+    const filesArray = fs.readdirSync(i18nDirPath);
+    // set search performance is supposed to be better than array
+    const files = new Set(filesArray.map(f => f.toLowerCase()));
+
+    /** @type {PackageStrings} */
+    const packageStrings = {};
+    this.locales.forEach(locale => {
+      const ext = supportedFileExts.find(({ ext }) => files.has(`${locale}.${ext}`));
+      if (!ext) return;
+
+      const filename = `${locale}.${ext.ext}`;
+      const filepath = path.join(i18nDirPath, filename);
+
+      const strings = fs.readFileSync(filepath, "utf8");
+      packageStrings[locale] = ext.parse(strings);
+    });
+    this.localisations.addPackage({
+      pkgName,
+      strings: packageStrings
+    });
+  }
+}
+
+class Localisations {
+  constructor() {
+    /** @type {Array<string>} */
+    this.locales = [];
+    /** @type {{ [k: string]: PackageLocalisations }} */
+    this.packages = {};
+  }
+
+  /**
+   * @param {object} opts
+   * @param {Array<string>} opts.locales
+   * @param {AllAstCache} [opts.asts]
+   */
+  initialise({ locales, asts }) {
+    this.locales = locales;
+    this.asts = asts;
+  }
+
+  /**
+   * @param {Key} keystr
+   * @param {Opts} opts
+   */
+  t(keystr, opts = {}) {
+    let key = keystr.split(".");
+    if (key.length < 2) return fallback(keystr, opts);
+
+    guardPrototypePollution(key);
+
+    const pkgName = key[0];
+    key = key.slice(1);
+    return this.packages[pkgName]?.t(key, opts) ?? fallback(keystr, opts);
+  }
+
+  /**
+   * @param {object} opts
+   * @param {string} opts.pkgName
+   * @param {PackageStrings} opts.strings
+   */
+  addPackage({ pkgName, strings }) {
+    this.packages[pkgName] = new PackageLocalisations({
+      locales: this.locales,
+      strings,
+      asts: this.asts?.[pkgName]
+    });
+  }
+}
+
+/**
+ * manages strings of all languages for a single package
+ * (in other words, manages `PackageLocalisations` instances)
+ */
+class PackageLocalisations {
+  /**
+   * @param {object} opts
+   * @param {Array<string>} opts.locales
+   * @param {PackageStrings} opts.strings
+   * @param {PackageASTCache} [opts.asts]
+   */
+  constructor({ locales, strings: _strings, asts }) {
+    this.locales = locales;
+    /** @type {PackageASTCache} */
+    this.asts = asts ?? {};
+    /** @type {{ [k: string]: SingleLanguageLocalisations }} */
+    this.localeObjs = {};
+
+    for (const [locale, strings] of Object.entries(_strings)) {
+      this.localeObjs[locale] = new SingleLanguageLocalisations({
+        locale,
+        strings,
+        asts: (this.asts[locale] = this.asts[locale] ?? { items: {} })
+      });
+    }
+  }
+
+  /**
+   * @param {SplitKey} key
+   * @param {Opts} opts
+   */
+  t(key, opts = {}) {
+    for (const locale of this.locales) {
+      const localised = this.localeObjs[locale]?.t(key, opts);
+      if (localised) return localised;
+    }
+  }
+}
+
+/**
+ * manages strings for a single locale of a single package
+ */
+// TODO someone please help me find a better name ~meadowsys
+class SingleLanguageLocalisations {
+  /**
+   * @param {object} opts
+   * @param {string} opts.locale
+   * @param {Strings} opts.strings
+   * @param {ASTCache} [opts.asts]
+   */
+  constructor({ locale, strings, asts }) {
+    this.locale = locale;
+    this.strings = strings;
+    /** @type {ASTCache} */
+    this.asts = asts ?? { items: {} };
+    /** @type {FormatterCache} */
+    this.formatters = {};
+  }
+
+  /**
+   * @param {SplitKey} key
+   * @param {Opts} opts
+   */
+  t(key, opts = {}) {
+    const formatter = this._getFormatter(key);
+    if (formatter) {
+      const formatted = /** @type {string} */ (formatter.format(opts));
+      return formatted;
+    }
+  }
+
+  /**
+   * @param {SplitKey} key
+   */
+  _getFormatter(key) {
+    let value = this.formatters;
+
+    const lastKeyPos = key.length - 1;
+    for (let i = 0; i < lastKeyPos; i++) {
+      const k = key[i];
+      const v = value[k];
+
+      if (!v) {
+        /** @type {FormatterCache} */
+        const cache = {};
+        value[k] = cache;
+        value = cache;
+        continue;
+      }
+      if (v instanceof IntlMessageFormat) return;
+      value = v;
+    }
+
+    const k = key[lastKeyPos];
+    const v = value[k];
+
+    if (!v) {
+      const ast = this._getAST(key);
+      if (!ast) return;
+
+      const formatter = new IntlMessageFormat(ast.ast, this.locale);
+      value[k] = formatter;
+      return formatter;
+    }
+
+    if (v instanceof IntlMessageFormat) return v;
+  }
+
+  /**
+   * @param {SplitKey} key
+   */
+  _getAST(key) {
+    let value = this.asts;
+
+    const lastKeyPos = key.length - 1;
+    for (let i = 0; i < lastKeyPos; i++) {
+      const k = key[i];
+      const v = value.items[k];
+
+      if (!v) {
+        /** @type {ManyASTs} */
+        const cache = { items: {} };
+        value[k] = cache;
+        value = cache;
+        continue;
+      }
+      if (isAST(v)) return;
+      value = v;
+    }
+
+    const k = key[lastKeyPos];
+    const v = value.items[k];
+
+    if (!v) {
+      const string = this._getString(key);
+      if (!string) return;
+
+      /** @type {AST} */
+      const ast = {
+        ast: parseToAST(string)
+      };
+
+      value.items[k] = ast;
+      return ast;
+    }
+
+    if (isAST(v)) return v;
+  }
+
+  /**
+   * @param {SplitKey} key
+   */
+  _getString(key) {
+    let value = this.strings;
+
+    const lastKeyPos = key.length - 1;
+    for (let i = 0; i < lastKeyPos; i++) {
+      const k = key[i];
+      const v = value[k];
+
+      if (!v || typeof v === "string") return;
+      value = v;
+    }
+
+    const k = key[lastKeyPos];
+    const v = value[k];
+    if (typeof v === "string") return v;
+  }
+}
+
+/**
+ * @param {OneOrManyASTs} obj
+ * @return {obj is AST}
+ */
+function isAST(obj) {
+  return "ast" in obj;
+}
+
+/**
+ * @param {SplitKey} key
+ */
+function guardPrototypePollution(key) {
+  if (key.includes("__proto__")) {
+    throw new Error(`prototype pollution in key "${key.join(".")}" was detected and prevented`);
+  }
+}
+
+/**
+ * @param {Key} keystr
+ * @param {Opts} opts
+ */
+function fallback(keystr, opts) {
+  const optsArray = Object.entries(opts);
+  if (optsArray.length === 0) return keystr;
+
+  return `${keystr}: { ${
+    optsArray
+      .map(([k, v]) => `${JSON.stringify(k)}: ${JSON.stringify(v)}`)
+      .join(", ")
+  } }`;
+}
+
+/**
+ * "basic" types
+ * @typedef {import("@formatjs/icu-messageformat-parser").MessageFormatElement} MessageFormatElement
+ * @typedef {{ ast: Array<MessageFormatElement> }} AST
+ * @typedef {{ items: { [k: string]: OneOrManyASTs } }} ManyASTs
+ * @typedef {AST | ManyASTs} OneOrManyASTs
+ *
+ * @typedef {string} Key
+ * @typedef {Array<string>} SplitKey
+ * @typedef {{ [k: string]: string }} Opts
+ */
+/**
+ * types for `Localisations`
+ * @typedef {{ [k: string]: PackageStrings }} AllStrings
+ * @typedef {{ [k: string]: PackageASTCache }} AllAstCache
+ */
+/**
+ * types for `PackageLocalisations`
+ * @typedef {{ [k: string]: Strings }} PackageStrings
+ * @typedef {{ [k: string]: ASTCache }} PackageASTCache
+ */
+/**
+ * used in `SingleLanguageLocalisations`
+ * @typedef {{ [k: string]: string | Strings }} Strings
+ * @typedef {ManyASTs} ASTCache
+ * @typedef {{ [k: string]: IntlMessageFormat | FormatterCache }} FormatterCache
+ */
diff --git a/src/package-manager.js b/src/package-manager.js
index 23a8e904dc..372276357c 100644
--- a/src/package-manager.js
+++ b/src/package-manager.js
@@ -38,7 +38,8 @@ module.exports = class PackageManager {
       grammarRegistry: this.grammarRegistry,
       deserializerManager: this.deserializerManager,
       viewRegistry: this.viewRegistry,
-      uriHandlerRegistry: this.uriHandlerRegistry
+      uriHandlerRegistry: this.uriHandlerRegistry,
+      i18n: this.i18n
     } = params);
 
     this.emitter = new Emitter();
@@ -587,7 +588,8 @@ module.exports = class PackageManager {
       menuManager: this.menuManager,
       contextMenuManager: this.contextMenuManager,
       deserializerManager: this.deserializerManager,
-      viewRegistry: this.viewRegistry
+      viewRegistry: this.viewRegistry,
+      i18n: this.i18n
     };
 
     pack = metadata.theme ? new ThemePackage(options) : new Package(options);
@@ -692,7 +694,8 @@ module.exports = class PackageManager {
       menuManager: this.menuManager,
       contextMenuManager: this.contextMenuManager,
       deserializerManager: this.deserializerManager,
-      viewRegistry: this.viewRegistry
+      viewRegistry: this.viewRegistry,
+      i18n: this.i18n
     };
 
     const pack = metadata.theme
diff --git a/src/package.js b/src/package.js
index 0071472dc2..db9534c6ad 100644
--- a/src/package.js
+++ b/src/package.js
@@ -30,6 +30,7 @@ module.exports = class Package {
     this.contextMenuManager = params.contextMenuManager;
     this.deserializerManager = params.deserializerManager;
     this.viewRegistry = params.viewRegistry;
+    this.i18n = params.i18n;
     this.emitter = new Emitter();
 
     this.mainModule = null;
@@ -45,6 +46,7 @@ module.exports = class Package {
       (this.metadata && this.metadata.name) ||
       params.name ||
       path.basename(this.path);
+    this.t = this.i18n.getT(this.name);
     this.reset();
   }
 
@@ -240,7 +242,10 @@ module.exports = class Package {
         }
         if (typeof this.mainModule.activate === 'function') {
           this.mainModule.activate(
-            this.packageManager.getPackageState(this.name) || {}
+            this.packageManager.getPackageState(this.name) || {},
+            {
+              t: this.t
+            }
           );
         }
         this.mainActivated = true;
diff --git a/yarn.lock b/yarn.lock
index 845064f393..9368b62924 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1431,6 +1431,45 @@
     minimatch "^3.1.2"
     strip-json-comments "^3.1.1"
 
+"@formatjs/ecma402-abstract@1.17.1":
+  version "1.17.1"
+  resolved "https://registry.yarnpkg.com/@formatjs/ecma402-abstract/-/ecma402-abstract-1.17.1.tgz#6ac7d6a1d1c9c8eff76ab6ed949f2a5cbe424030"
+  integrity sha512-N2sjSUrmsEoynG8Q61pkrKlJ9PxcUGxJke1x3301aGyprGgl58wHWhgGUnzTfS4OHNNNQDxzjcXVp1t5fGW6yQ==
+  dependencies:
+    "@formatjs/intl-localematcher" "0.4.1"
+    tslib "^2.4.0"
+
+"@formatjs/fast-memoize@2.2.0":
+  version "2.2.0"
+  resolved "https://registry.yarnpkg.com/@formatjs/fast-memoize/-/fast-memoize-2.2.0.tgz#33bd616d2e486c3e8ef4e68c99648c196887802b"
+  integrity sha512-hnk/nY8FyrL5YxwP9e4r9dqeM6cAbo8PeU9UjyXojZMNvVad2Z06FAVHyR3Ecw6fza+0GH7vdJgiKIVXTMbSBA==
+  dependencies:
+    tslib "^2.4.0"
+
+"@formatjs/icu-messageformat-parser@2.6.1", "@formatjs/icu-messageformat-parser@^2.6.1":
+  version "2.6.1"
+  resolved "https://registry.yarnpkg.com/@formatjs/icu-messageformat-parser/-/icu-messageformat-parser-2.6.1.tgz#ca497d5a2bff641dc0978bd9b64d1d02597980cb"
+  integrity sha512-dTDNupwdovxT1xDXC96zzPUua/XrxTQTOulJZSvaJP0pt3rr/cGR/tq4d7BnxY9oqPZpc4fjWBmrRlhcUyBSiw==
+  dependencies:
+    "@formatjs/ecma402-abstract" "1.17.1"
+    "@formatjs/icu-skeleton-parser" "1.6.1"
+    tslib "^2.4.0"
+
+"@formatjs/icu-skeleton-parser@1.6.1":
+  version "1.6.1"
+  resolved "https://registry.yarnpkg.com/@formatjs/icu-skeleton-parser/-/icu-skeleton-parser-1.6.1.tgz#3647f41b82e362c08bb80bd9b653c7eb6ff31118"
+  integrity sha512-/LQ6ovxYd8FQjVLmbV+WmuFy86o+JTc0cIQuWixuLuUMfRRif8eUQw3vPK5hx7C/g1UVmKAaOcYRTEsvyEGz9g==
+  dependencies:
+    "@formatjs/ecma402-abstract" "1.17.1"
+    tslib "^2.4.0"
+
+"@formatjs/intl-localematcher@0.4.1":
+  version "0.4.1"
+  resolved "https://registry.yarnpkg.com/@formatjs/intl-localematcher/-/intl-localematcher-0.4.1.tgz#af63e2c065731a33f6fed36dc85058009a7f8062"
+  integrity sha512-Fs4MhhHlLC0RrspX2u2KP7zlwL9eHrBZsOBxaPOeqrCZYLaOUK4cYXQ1ErpAB0HnGV/GUXNa5smzV/7jCuRzxg==
+  dependencies:
+    tslib "^2.4.0"
+
 "@gar/promisify@^1.0.1":
   version "1.1.3"
   resolved "https://registry.yarnpkg.com/@gar/promisify/-/promisify-1.1.3.tgz#555193ab2e3bb3b6adc3d551c9c030d9e860daf6"
@@ -1895,7 +1934,6 @@ abbrev@1:
   version "1.9.1"
   dependencies:
     etch "^0.14.1"
-    semver "^7.3.8"
 
 acorn-jsx@^5.3.2:
   version "5.3.2"
@@ -5484,6 +5522,16 @@ interpret@^1.0.0:
   resolved "https://registry.yarnpkg.com/interpret/-/interpret-1.4.0.tgz#665ab8bc4da27a774a40584e812e3e0fa45b1a1e"
   integrity sha512-agE4QfB2Lkp9uICn7BAqoscw4SZP9kTE2hxiFI3jBPmXJfdqiahTbUuKGsMoN2GtqL9AxhYioAcVvgsb1HvRbA==
 
+intl-messageformat@^10.5.1:
+  version "10.5.1"
+  resolved "https://registry.yarnpkg.com/intl-messageformat/-/intl-messageformat-10.5.1.tgz#40304cbde01c8cb2236e11ac8c827642bed474d0"
+  integrity sha512-irEmjxHq0f1MHviQr3Q4ToF9EgYbnXDq2/R9MRTTveGKHgy6VZ29hQxswu4trqWaX7T6njKxSoKVG92OSz0U5Q==
+  dependencies:
+    "@formatjs/ecma402-abstract" "1.17.1"
+    "@formatjs/fast-memoize" "2.2.0"
+    "@formatjs/icu-messageformat-parser" "2.6.1"
+    tslib "^2.4.0"
+
 invert-kv@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/invert-kv/-/invert-kv-1.0.0.tgz#104a8e4aaca6d3d8cd157a8ef8bfab2d7a3ffdb6"
@@ -9497,6 +9545,11 @@ tslib@^2.3.0:
   resolved "https://registry.yarnpkg.com/tslib/-/tslib-2.6.0.tgz#b295854684dbda164e181d259a22cd779dcd7bc3"
   integrity sha512-7At1WUettjcSRHXCyYtTselblcHl9PJFFVKiCAy/bY97+BPZXSQ2wbq0P9s8tK2G7dFQfNnlJnPAiArVBVBsfA==
 
+tslib@^2.4.0:
+  version "2.6.2"
+  resolved "https://registry.yarnpkg.com/tslib/-/tslib-2.6.2.tgz#703ac29425e7b37cd6fd456e92404d46d1f3e4ae"
+  integrity sha512-AEYxH93jGFPn/a2iVAwW87VuUIkR1FVUKB77NwMF7nBTDkDrrT/Hpt/IrCJ0QXhW27jTBDcf5ZY7w6RiqTMw2Q==
+
 tunnel-agent@^0.6.0:
   version "0.6.0"
   resolved "https://registry.yarnpkg.com/tunnel-agent/-/tunnel-agent-0.6.0.tgz#27a5dea06b36b04a0a9966774b290868f0fc40fd"