diff --git a/docs/source/index.rst b/docs/source/index.rst
index c5db42fdc6..82b70e684f 100644
--- a/docs/source/index.rst
+++ b/docs/source/index.rst
@@ -22,6 +22,7 @@ Pyro Documentation
    optimization
    poutine
    ops
+   settings
    testing
 
 .. toctree::
diff --git a/docs/source/settings.rst b/docs/source/settings.rst
new file mode 100644
index 0000000000..e2cd61fd9d
--- /dev/null
+++ b/docs/source/settings.rst
@@ -0,0 +1,6 @@
+Settings
+--------
+
+.. automodule:: pyro.settings
+   :members:
+   :member-order: bysource
diff --git a/pyro/__init__.py b/pyro/__init__.py
index c8c07e6eb2..b92471913e 100644
--- a/pyro/__init__.py
+++ b/pyro/__init__.py
@@ -25,6 +25,8 @@
 )
 from pyro.util import set_rng_seed
 
+from . import settings
+
 # After changing this, run scripts/update_version.py
 version_prefix = "1.8.2"
 
@@ -58,6 +60,7 @@
     "render_model",
     "sample",
     "set_rng_seed",
+    "settings",
     "subsample",
     "validation_enabled",
 ]
diff --git a/pyro/distributions/torch.py b/pyro/distributions/torch.py
index 9459803212..c6e8c7e1d2 100644
--- a/pyro/distributions/torch.py
+++ b/pyro/distributions/torch.py
@@ -9,6 +9,7 @@
 from pyro.distributions.util import broadcast_shape, sum_rightmost
 from pyro.ops.special import log_binomial
 
+from .. import settings
 from . import constraints
 
 
@@ -98,6 +99,22 @@ def log_prob(self, value):
         )
 
 
+@settings.register(
+    "binomial_approx_sample_thresh", __name__, "Binomial.approx_sample_thresh"
+)
+def _validate_thresh(thresh):
+    assert isinstance(thresh, float)
+    assert 0 < thresh
+
+
+@settings.register(
+    "binomial_approx_log_prob_tol", __name__, "Binomial.approx_log_prob_tol"
+)
+def _validate_tol(tol):
+    assert isinstance(tol, float)
+    assert 0 <= tol
+
+
 # This overloads .log_prob() and .enumerate_support() to speed up evaluating
 # log_prob on the support of this variable: we can completely avoid tensor ops
 # and merely reshape the self.logits tensor. This is especially important for
diff --git a/pyro/distributions/util.py b/pyro/distributions/util.py
index f3ddbf51a2..ba59273069 100644
--- a/pyro/distributions/util.py
+++ b/pyro/distributions/util.py
@@ -15,9 +15,18 @@
 
 from pyro.util import ignore_jit_warnings
 
+from .. import settings
+
 _VALIDATION_ENABLED = __debug__
 torch_dist.Distribution.set_default_validate_args(__debug__)
 
+settings.register("validate_distributions_pyro", __name__, "_VALIDATION_ENABLED")
+settings.register(
+    "validate_distributions_torch",
+    "torch.distributions.distribution",
+    "Distribution._validate_args",
+)
+
 log_sum_exp = logsumexp  # DEPRECATED
 
 
diff --git a/pyro/infer/util.py b/pyro/infer/util.py
index 3ee94b884d..7ea460c1ec 100644
--- a/pyro/infer/util.py
+++ b/pyro/infer/util.py
@@ -16,7 +16,11 @@
 from pyro.ops.rings import MarginalRing
 from pyro.poutine.util import site_is_subsample
 
+from .. import settings
+
 _VALIDATION_ENABLED = __debug__
+settings.register("validate_infer", __name__, "_VALIDATION_ENABLED")
+
 LAST_CACHE_SIZE = [Counter()]  # for profiling
 
 
diff --git a/pyro/ops/tensor_utils.py b/pyro/ops/tensor_utils.py
index f820aa72cf..17cb367a17 100644
--- a/pyro/ops/tensor_utils.py
+++ b/pyro/ops/tensor_utils.py
@@ -6,10 +6,18 @@
 import torch
 from torch.fft import irfft, rfft
 
+from .. import settings
+
 _ROOT_TWO_INVERSE = 1.0 / math.sqrt(2.0)
 CHOLESKY_RELATIVE_JITTER = 4.0  # in units of finfo.eps
 
 
+@settings.register("cholesky_relative_jitter", __name__, "CHOLESKY_RELATIVE_JITTER")
+def _validate_jitter(value):
+    assert isinstance(value, (float, int))
+    assert 0 <= value
+
+
 def as_complex(x):
     """
     Similar to :func:`torch.view_as_complex` but copies data in case strides
diff --git a/pyro/poutine/util.py b/pyro/poutine/util.py
index e90c2a5917..3a0ec0316b 100644
--- a/pyro/poutine/util.py
+++ b/pyro/poutine/util.py
@@ -1,7 +1,10 @@
 # Copyright (c) 2017-2019 Uber Technologies, Inc.
 # SPDX-License-Identifier: Apache-2.0
 
+from .. import settings
+
 _VALIDATION_ENABLED = __debug__
+settings.register("validate_poutine", __name__, "_VALIDATION_ENABLED")
 
 
 def enable_validation(is_validate):
diff --git a/pyro/settings.py b/pyro/settings.py
new file mode 100644
index 0000000000..38dc1e01de
--- /dev/null
+++ b/pyro/settings.py
@@ -0,0 +1,163 @@
+# Copyright Contributors to the Pyro project.
+# SPDX-License-Identifier: Apache-2.0
+
+"""
+Example usage::
+
+    # Simple getting and setting.
+    print(pyro.settings.get())  # print all settings
+    print(pyro.settings.get("cholesky_relative_jitter"))  # print one
+    pyro.settings.set(cholesky_relative_jitter=0.5)  # set one
+    pyro.settings.set(**my_settings)  # set many
+
+    # Use as a contextmanager.
+    with pyro.settings.context(cholesky_relative_jitter=0.5):
+        my_function()
+
+    # Use as a decorator.
+    fn = pyro.settings.context(cholesky_relative_jitter=0.5)(my_function)
+    fn()
+
+    # Register a new setting.
+    pyro.settings.register(
+        "binomial_approx_sample_thresh",  # alias
+        "pyro.distributions.torch",       # module
+        "Binomial.approx_sample_thresh",  # deep name
+    )
+
+    # Register a new setting on a user-provided validator.
+    @pyro.settings.register(
+        "binomial_approx_sample_thresh",  # alias
+        "pyro.distributions.torch",       # module
+        "Binomial.approx_sample_thresh",  # deep name
+    )
+    def validate_thresh(thresh):  # called each time setting is set
+        assert isinstance(thresh, float)
+        assert thresh > 0
+
+Default Settings
+----------------
+
+{defaults}
+
+Settings Interface
+------------------
+"""
+
+# This library must have no dependencies on other pyro modules.
+import functools
+from contextlib import contextmanager
+from importlib import import_module
+from typing import Any, Callable, Dict, Iterator, Optional, Tuple
+
+# Docs are updated by register().
+_doc_template = __doc__
+
+# Global registry mapping alias:str to (modulename, deepname, validator)
+# triples where deepname may have dots to indicate e.g. class variables.
+_REGISTRY: Dict[str, Tuple[str, str, Optional[Callable]]] = {}
+
+
+def get(alias: Optional[str] = None) -> Any:
+    """
+    Gets one or all global settings.
+
+    :param str alias: The name of a registered setting.
+    :returns: The currently set value.
+    """
+    if alias is None:
+        # Return dict of all settings.
+        return {alias: get(alias) for alias in sorted(_REGISTRY)}
+    # Get a single setting.
+    module, deepname, validator = _REGISTRY[alias]
+    value = import_module(module)
+    for name in deepname.split("."):
+        value = getattr(value, name)
+    return value
+
+
+def set(**kwargs) -> None:
+    r"""
+    Sets one or more settings.
+
+    :param \*\*kwargs: alias=value pairs.
+    """
+    for alias, value in kwargs.items():
+        module, deepname, validator = _REGISTRY[alias]
+        if validator is not None:
+            validator(value)
+        destin = import_module(module)
+        names = deepname.split(".")
+        for name in names[:-1]:
+            destin = getattr(destin, name)
+        setattr(destin, names[-1], value)
+
+
+@contextmanager
+def context(**kwargs) -> Iterator[None]:
+    r"""
+    Context manager to temporarily override one or more settings. This also
+    works as a decorator.
+
+    :param \*\*kwargs: alias=value pairs.
+    """
+    old = {alias: get(alias) for alias in kwargs}
+    try:
+        set(**kwargs)
+        yield
+    finally:
+        set(**old)
+
+
+def register(
+    alias: str,
+    modulename: str,
+    deepname: str,
+    validator: Optional[Callable] = None,
+) -> Callable:
+    """
+    Register a global settings.
+
+    This should be declared in the module where the setting is defined.
+
+    This can be used either as a declaration::
+
+        settings.register("my_setting", __name__, "MY_SETTING")
+
+    or as a decorator on a user-defined validator function::
+
+        @settings.register("my_setting", __name__, "MY_SETTING")
+        def _validate_my_setting(value):
+            assert isinstance(value, float)
+            assert 0 < value
+
+    :param str alias: A valid python identifier serving as a settings alias.
+        Lower snake case preferred, e.g. ``my_setting``.
+    :param str modulename: The module name where the setting is declared,
+        typically ``__name__``.
+    :param str deepname: A ``.``-separated string of names. E.g. for a module
+        constant, use ``MY_CONSTANT``. For a class attributue, use
+        ``MyClass.my_attribute``.
+    :param callable validator: Optional validator that inputs a value,
+        possibly raises validation errors, and returns None.
+    """
+    global __doc__
+    assert isinstance(alias, str)
+    assert alias.isidentifier()
+    assert isinstance(modulename, str)
+    assert isinstance(deepname, str)
+    _REGISTRY[alias] = modulename, deepname, validator
+
+    # Add default value to module docstring.
+    __doc__ = _doc_template.format(
+        defaults="\n".join(f"- {a} = {get(a)}" for a in sorted(_REGISTRY))
+    )
+
+    # Support use as a decorator on an optional user-provided validator.
+    if validator is None:
+        # Return a decorator, but its fine if user discards this.
+        return functools.partial(register, alias, modulename, deepname)
+    else:
+        # Test current value passes validation.
+        validator(get(alias))
+        return validator
diff --git a/tests/test_settings.py b/tests/test_settings.py
new file mode 100644
index 0000000000..fa584b7aa9
--- /dev/null
+++ b/tests/test_settings.py
@@ -0,0 +1,50 @@
+# Copyright Contributors to the Pyro project.
+# SPDX-License-Identifier: Apache-2.0
+
+import pytest
+
+from pyro import settings
+
+_TEST_SETTING: float = 0.1
+
+pytestmark = pytest.mark.stage("unit")
+
+
+def test_settings():
+    v0 = settings.get()
+    assert isinstance(v0, dict)
+    assert all(isinstance(alias, str) for alias in v0)
+    assert settings.get("validate_distributions_pyro") is True
+    assert settings.get("validate_distributions_torch") is True
+    assert settings.get("validate_poutine") is True
+    assert settings.get("validate_infer") is True
+
+
+def test_register():
+    with pytest.raises(KeyError):
+        settings.get("test_setting")
+
+    @settings.register("test_setting", "tests.test_settings", "_TEST_SETTING")
+    def _validate(value):
+        assert isinstance(value, float)
+        assert 0 < value
+
+    # Test simple get and set.
+    assert settings.get("test_setting") == 0.1
+    settings.set(test_setting=0.2)
+    assert settings.get("test_setting") == 0.2
+    with pytest.raises(AssertionError):
+        settings.set(test_setting=-0.1)
+
+    # Test context manager.
+    with settings.context(test_setting=0.3):
+        assert settings.get("test_setting") == 0.3
+    assert settings.get("test_setting") == 0.2
+
+    # Test decorator.
+    @settings.context(test_setting=0.4)
+    def fn():
+        assert settings.get("test_setting") == 0.4
+
+    fn()
+    assert settings.get("test_setting") == 0.2