diff --git a/README.md b/README.md
index bd5d90d72..7aeab4097 100644
--- a/README.md
+++ b/README.md
@@ -137,6 +137,20 @@ Built-in rules for creating optimized container images:
 bazel_dep(name = "aspect_rules_py", version = "1.11.2")
 ```
 
+### Requirements
+
+The minimum supported Python version is **3.10**. The launcher, test runners, and build
+tools that run under your configured interpreter use 3.10 syntax, and CI only exercises
+3.10 and newer. Older interpreters can still be fetched via `interpreters.configure()`,
+but `py_binary` and `py_test` targets will fail at startup on them.
+
+Some `uv` features need newer versions:
+
+| Feature                                                                                                                 | Python |
+| ----------------------------------------------------------------------------------------------------------------------- | ------ |
+| Free-threaded interpreters (`freethreaded = True`), [first shipped in CPython 3.13](https://peps.python.org/pep-0703/) | 3.13+  |
+| `pyproject.toml` parsing in sdist native-dependency detection (needs stdlib `tomllib`)                                  | 3.11+  |
+
 ### Quick Start
 
 Load rules from `aspect_rules_py` in your `BUILD` files:
diff --git a/docs/interpreter.md b/docs/interpreter.md
index c3c9e15e1..e3e9cc74b 100644
--- a/docs/interpreter.md
+++ b/docs/interpreter.md
@@ -14,8 +14,10 @@ are discovered automatically from PBS release artifacts and cached in your
 it — no repinning, no manifest regeneration.
 
 **No editorial decisions.** We don't decide which Python versions you can use.
-Any version published in a PBS release is available. Need Python 3.8? Add an
-older release date that includes it.
+Any version published in a PBS release is available. Need a version that newer
+releases dropped? Add an older release date that includes it. Note that the
+rules themselves require Python 3.10 or newer at runtime (see
+[Requirements](../README.md#requirements)).
 
 **Windows and cross-platform support.** 9 platforms are registered out of the
 box, including Windows (x86_64, aarch64, i686), Linux (glibc and musl), and
@@ -65,7 +67,7 @@ interpreters.configure(
 )
 
 interpreters.toolchain(python_version = "3.12")
-interpreters.toolchain(python_version = "3.8")  # Resolved from 20241002
+interpreters.toolchain(python_version = "3.10")  # Resolved from 20241002 once newer releases drop it
 
 use_repo(interpreters, "python_interpreters")
 register_toolchains("@python_interpreters//:all")
diff --git a/pyproject.toml b/pyproject.toml
index eb142bf1f..c1e9870f1 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -30,7 +30,7 @@ dev-dependencies = [
 ]
 
 [tool.ruff]
-target-version = "py39"
+target-version = "py310"
 extend-exclude = [
    # Intentionally unparsable .py-as-data fixture.
    "py/tests/py-venv-multi-exec/broken_data.py",