diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-08-11-13-50-35.gh-issue-155504.PsTqZm.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-08-11-13-50-35.gh-issue-155504.PsTqZm.rst
new file mode 100644
index 000000000000000..e042bf3554e6f05
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-08-11-13-50-35.gh-issue-155504.PsTqZm.rst
@@ -0,0 +1,2 @@
+Fix a crash when thread state creation fails before the thread state is fully
+initialized.
diff --git a/Python/pystate.c b/Python/pystate.c
index d1505be4acf50f2..5de6defb4bdc3ef 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -1506,6 +1506,8 @@ alloc_threadstate(PyInterpreterState *interp)
         }
         reset_threadstate(tstate);
     }
+    // Set the interpreter before any later initialization can fail.
+    tstate->base.interp = interp;
     return tstate;
 }