diff --git a/Lib/idlelib/pyshell.py b/Lib/idlelib/pyshell.py
index e68233a5a4131e..6def8935a64ef3 100755
--- a/Lib/idlelib/pyshell.py
+++ b/Lib/idlelib/pyshell.py
@@ -1688,9 +1688,15 @@ def main():
         if prefer_tabs_preference_warning:
             shell.show_warning(prefer_tabs_preference_warning)
 
-    while flist.inversedict:  # keep IDLE running while files are open.
-        root.mainloop()
-    root.destroy()
+    try:
+        while flist.inversedict:  # keep IDLE running while files are open.
+            root.mainloop()
+    finally:
+        try:
+            root.destroy()
+        finally:
+            import _tkinter
+            _tkinter._finalize_tcl()
     capture_warnings(False)
 
 if __name__ == "__main__":
diff --git a/Misc/NEWS.d/next/IDLE/2021-05-16-16-24-31.bpo-40452.Nayfdf.rst b/Misc/NEWS.d/next/IDLE/2021-05-16-16-24-31.bpo-40452.Nayfdf.rst
new file mode 100644
index 00000000000000..904bc8940d3190
--- /dev/null
+++ b/Misc/NEWS.d/next/IDLE/2021-05-16-16-24-31.bpo-40452.Nayfdf.rst
@@ -0,0 +1 @@
+Fix new clipboard content copied from IDLE being gone after exiting IDLE.
diff --git a/Modules/_tkinter.c b/Modules/_tkinter.c
index 20e01c79668549..3e70aa0a41ed94 100644
--- a/Modules/_tkinter.c
+++ b/Modules/_tkinter.c
@@ -3039,6 +3039,24 @@ _tkinter_getbusywaitinterval_impl(PyObject *module)
     return Tkinter_busywaitinterval;
 }
 
+/*[clinic input]
+_tkinter._finalize_tcl
+
+Finalize the Tcl interpreter.
+
+This should be called just before an app exits, to allow Tcl to
+execute its own finalization logic. After this, tkinter can no
+longer be used, and attempts to do so will result in errors.
+[clinic start generated code]*/
+
+static PyObject *
+_tkinter__finalize_tcl_impl(PyObject *module)
+/*[clinic end generated code: output=a7a2a4c67f43bd28 input=e1082c1b262a40aa]*/
+{
+    Tcl_FinalizeThread();
+    Py_RETURN_NONE;
+}
+
 #include "clinic/_tkinter.c.h"
 
 static PyMethodDef Tktt_methods[] =
@@ -3122,6 +3140,7 @@ static PyMethodDef moduleMethods[] =
     _TKINTER_CREATE_METHODDEF
     _TKINTER_SETBUSYWAITINTERVAL_METHODDEF
     _TKINTER_GETBUSYWAITINTERVAL_METHODDEF
+    _TKINTER__FINALIZE_TCL_METHODDEF
     {NULL,                 NULL}
 };
 
diff --git a/Modules/clinic/_tkinter.c.h b/Modules/clinic/_tkinter.c.h
index 96c6ee26f426c3..a68f9e11ec947c 100644
--- a/Modules/clinic/_tkinter.c.h
+++ b/Modules/clinic/_tkinter.c.h
@@ -858,6 +858,28 @@ _tkinter_getbusywaitinterval(PyObject *module, PyObject *Py_UNUSED(ignored))
     return return_value;
 }
 
+PyDoc_STRVAR(_tkinter__finalize_tcl__doc__,
+"_finalize_tcl($module, /)\n"
+"--\n"
+"\n"
+"Finalize the Tcl interpreter.\n"
+"\n"
+"This should be called just before an app exits, to allow Tcl to\n"
+"execute its own finalization logic. After this, tkinter can no\n"
+"longer be used, and attempts to do so will result in errors.");
+
+#define _TKINTER__FINALIZE_TCL_METHODDEF    \
+    {"_finalize_tcl", (PyCFunction)_tkinter__finalize_tcl, METH_NOARGS, _tkinter__finalize_tcl__doc__},
+
+static PyObject *
+_tkinter__finalize_tcl_impl(PyObject *module);
+
+static PyObject *
+_tkinter__finalize_tcl(PyObject *module, PyObject *Py_UNUSED(ignored))
+{
+    return _tkinter__finalize_tcl_impl(module);
+}
+
 #ifndef _TKINTER_TKAPP_CREATEFILEHANDLER_METHODDEF
     #define _TKINTER_TKAPP_CREATEFILEHANDLER_METHODDEF
 #endif /* !defined(_TKINTER_TKAPP_CREATEFILEHANDLER_METHODDEF) */
@@ -865,4 +887,4 @@ _tkinter_getbusywaitinterval(PyObject *module, PyObject *Py_UNUSED(ignored))
 #ifndef _TKINTER_TKAPP_DELETEFILEHANDLER_METHODDEF
     #define _TKINTER_TKAPP_DELETEFILEHANDLER_METHODDEF
 #endif /* !defined(_TKINTER_TKAPP_DELETEFILEHANDLER_METHODDEF) */
-/*[clinic end generated code: output=2a4e3bf8448604b5 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=3f82bafa92d88b20 input=a9049054013a1b77]*/