diff --git a/ax/core/auxiliary.py b/ax/core/auxiliary.py
new file mode 100644
index 00000000000..507af38025c
--- /dev/null
+++ b/ax/core/auxiliary.py
@@ -0,0 +1,41 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+# pyre-strict
+
+from __future__ import annotations
+
+from typing import Optional, TYPE_CHECKING
+
+from ax.core.data import Data
+from ax.utils.common.base import SortableBase
+
+
+if TYPE_CHECKING:
+    # import as module to make sphinx-autodoc-typehints happy
+    from ax import core  # noqa F401
+
+
+class AuxiliaryExperiment(SortableBase):
+    """Class for defining an auxiliary experiment."""
+
+    def __init__(
+        self,
+        experiment: core.experiment.Experiment,
+        data: Optional[Data] = None,
+    ) -> None:
+        """
+        Lightweight container of an experiment, and its data,
+        that will be used as auxiliary information for another experiment.
+        """
+        self.experiment = experiment
+        self.data: Data = data or experiment.lookup_data()
+
+    def _unique_id(self) -> str:
+        # While there can be multiple `AuxiliarySource`-s made from the same
+        # experiment (and thus sharing the experiment name), the uniqueness
+        # here is only needed w.r.t. parent object ("main experiment", for which
+        # this will be an auxiliary source for).
+        return self.experiment.name
diff --git a/ax/core/tests/test_auxiliary.py b/ax/core/tests/test_auxiliary.py
new file mode 100644
index 00000000000..8a816f6a1a7
--- /dev/null
+++ b/ax/core/tests/test_auxiliary.py
@@ -0,0 +1,24 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+from ax.core.auxiliary import AuxiliaryExperiment
+from ax.utils.common.testutils import TestCase
+from ax.utils.testing.core_stubs import get_experiment, get_experiment_with_data
+
+
+class AuxiliaryExperimentTest(TestCase):
+    def test_AuxiliaryExperiment(self) -> None:
+        for get_exp_func in [get_experiment, get_experiment_with_data]:
+            exp = get_exp_func()
+            data = exp.lookup_data()
+
+            # Test init
+            aux_exp = AuxiliaryExperiment(experiment=exp)
+            self.assertEqual(aux_exp.experiment, exp)
+            self.assertEqual(aux_exp.data, data)
+
+            aux_exp = AuxiliaryExperiment(experiment=exp, data=exp.lookup_data())
+            self.assertEqual(aux_exp.experiment, exp)
+            self.assertEqual(aux_exp.data, data)
diff --git a/ax/core/tests/test_experiment.py b/ax/core/tests/test_experiment.py
index de450f0f84c..0f2dfcda85f 100644
--- a/ax/core/tests/test_experiment.py
+++ b/ax/core/tests/test_experiment.py
@@ -11,11 +11,10 @@
 from unittest.mock import MagicMock, patch
 
 import pandas as pd
-from ax.core import BatchTrial, Trial
+from ax.core import BatchTrial, Experiment, Trial
 from ax.core.arm import Arm
 from ax.core.base_trial import TrialStatus
 from ax.core.data import Data
-from ax.core.experiment import Experiment
 from ax.core.map_data import MapData
 from ax.core.map_metric import MapMetric
 from ax.core.metric import Metric
diff --git a/ax/storage/json_store/encoders.py b/ax/storage/json_store/encoders.py
index 34c74336652..6b46d0bfdf3 100644
--- a/ax/storage/json_store/encoders.py
+++ b/ax/storage/json_store/encoders.py
@@ -12,11 +12,11 @@
 from typing import Any
 
 from ax.benchmark.problems.hpo.torchvision import PyTorchCNNTorchvisionBenchmarkProblem
-from ax.core import ObservationFeatures
+from ax.core import Experiment, ObservationFeatures
 from ax.core.arm import Arm
+from ax.core.auxiliary import AuxiliaryExperiment
 from ax.core.batch_trial import BatchTrial
 from ax.core.data import Data
-from ax.core.experiment import Experiment
 from ax.core.generator_run import GeneratorRun
 from ax.core.map_data import MapData, MapKeyInfo
 from ax.core.metric import Metric
@@ -710,6 +710,16 @@ def risk_measure_to_dict(
     }
 
 
+def auxiliary_experiment_to_dict(
+    auxiliary_experiment: AuxiliaryExperiment,
+) -> dict[str, Any]:
+    return {
+        "__type": auxiliary_experiment.__class__.__name__,
+        "experiment": auxiliary_experiment.experiment,
+        "data": auxiliary_experiment.data,
+    }
+
+
 def pathlib_to_dict(path: Path) -> dict[str, Any]:
     return {"__type": path.__class__.__name__, "pathsegments": [str(path)]}
 
diff --git a/ax/storage/json_store/registry.py b/ax/storage/json_store/registry.py
index 98e3b2d6b92..46ee42b8d6c 100644
--- a/ax/storage/json_store/registry.py
+++ b/ax/storage/json_store/registry.py
@@ -25,8 +25,9 @@
 )
 from ax.benchmark.runners.botorch_test import BotorchTestProblemRunner
 from ax.benchmark.runners.surrogate import SurrogateRunner
-from ax.core import ObservationFeatures
+from ax.core import Experiment, ObservationFeatures
 from ax.core.arm import Arm
+from ax.core.auxiliary import AuxiliaryExperiment
 from ax.core.base_trial import TrialStatus
 from ax.core.batch_trial import (
     AbandonedArm,
@@ -35,7 +36,7 @@
     LifecycleStage,
 )
 from ax.core.data import Data
-from ax.core.experiment import DataType, Experiment
+from ax.core.experiment import DataType
 from ax.core.generator_run import GeneratorRun
 from ax.core.map_data import MapData, MapKeyInfo
 from ax.core.map_metric import MapMetric
@@ -116,6 +117,7 @@
 )
 from ax.storage.json_store.encoders import (
     arm_to_dict,
+    auxiliary_experiment_to_dict,
     batch_to_dict,
     best_model_selector_to_dict,
     botorch_component_to_dict,
@@ -181,6 +183,7 @@
 #  avoid runtime subscripting errors.
 CORE_ENCODER_REGISTRY: dict[type, Callable[[Any], dict[str, Any]]] = {
     Arm: arm_to_dict,
+    AuxiliaryExperiment: auxiliary_experiment_to_dict,
     AndEarlyStoppingStrategy: logical_early_stopping_strategy_to_dict,
     AugmentedBraninMetric: metric_to_dict,
     AugmentedHartmann6Metric: metric_to_dict,
@@ -293,6 +296,7 @@
     "AugmentedBraninMetric": AugmentedBraninMetric,
     "AugmentedHartmann6Metric": AugmentedHartmann6Metric,
     "AutoTransitionAfterGen": AutoTransitionAfterGen,
+    "AuxiliaryExperiment": AuxiliaryExperiment,
     "Arm": Arm,
     "AggregatedBenchmarkResult": AggregatedBenchmarkResult,
     "BatchTrial": BatchTrial,
diff --git a/ax/storage/json_store/tests/test_json_store.py b/ax/storage/json_store/tests/test_json_store.py
index 7b78fbf7fba..02e84bc9326 100644
--- a/ax/storage/json_store/tests/test_json_store.py
+++ b/ax/storage/json_store/tests/test_json_store.py
@@ -59,6 +59,7 @@
     get_arm,
     get_augmented_branin_metric,
     get_augmented_hartmann_metric,
+    get_auxiliary_experiment,
     get_batch_trial,
     get_botorch_model,
     get_botorch_model_with_default_acquisition_class,
@@ -141,6 +142,7 @@
     ("Arm", get_arm),
     ("AugmentedBraninMetric", get_augmented_branin_metric),
     ("AugmentedHartmannMetric", get_augmented_hartmann_metric),
+    ("AuxiliaryExperiment", get_auxiliary_experiment),
     ("BatchTrial", get_batch_trial),
     ("BenchmarkMethod", get_sobol_gpei_benchmark_method),
     ("BenchmarkProblem", get_single_objective_benchmark_problem),
diff --git a/ax/utils/testing/core_stubs.py b/ax/utils/testing/core_stubs.py
index 8d9b836696c..5d9caa3fbe1 100644
--- a/ax/utils/testing/core_stubs.py
+++ b/ax/utils/testing/core_stubs.py
@@ -20,6 +20,7 @@
 import pandas as pd
 import torch
 from ax.core.arm import Arm
+from ax.core.auxiliary import AuxiliaryExperiment
 from ax.core.base_trial import BaseTrial, TrialStatus
 from ax.core.batch_trial import AbandonedArm, BatchTrial
 from ax.core.data import Data
@@ -879,6 +880,10 @@ def get_high_dimensional_branin_experiment(with_batch: bool = False) -> Experime
     return exp
 
 
+def get_auxiliary_experiment() -> AuxiliaryExperiment:
+    return AuxiliaryExperiment(experiment=get_experiment_with_data())
+
+
 ##############################
 # Search Spaces
 ##############################
diff --git a/sphinx/source/core.rst b/sphinx/source/core.rst
index 85ad971d468..9075d61d693 100644
--- a/sphinx/source/core.rst
+++ b/sphinx/source/core.rst
@@ -52,6 +52,15 @@ Core Classes
     :undoc-members:
     :show-inheritance:
 
+
+`AuxiliaryExperiment`
+~~~~~~~~~~~~
+
+.. automodule:: ax.core.auxiliary
+    :members:
+    :undoc-members:
+    :show-inheritance:
+
 `GenerationStrategyInterface`
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~