According to Jython's (a little dated) FAQ <https://wiki.python.org/jython/JythonFaq/GeneralInfo>, "Jython is approximately as fast as CPython--sometimes faster, sometimes slower. Because most JVMs--certainly the fastest ones--do long running, hot code will run faster over time."

PyPy aims to be (and is in many cases) faster than CPython.

The advantage with Jython isn't a performance one: it's the ability to call Java code directly.

Jython is usually slower than CPython I believe, it has no GIL though.

Wonder if it can be faster under higher parallelism conditions. Multiple threads doing some CPU intensive work?

Jython can utilize threads as well as Java can, so on many core machine Jython wins by a pretty large margin.