Joanne Fenn née Mersh, (born October 19, 1974) is an English middle distance athlete.

Joanne was born in Leytonstone, London and showed a great deal of promise in her early athletics career, but a series of injuries and an interest with a local band, The Business, halted her career.

After renewing her relationship with running Joanne continued to improve, but despite running a personal best of 1:59.86 at the 2002 Commonwealth Games, in Manchester, England, Joanne could only manage 7th place in the final.

2004 started promisingly for Jo with an 800 m. bronze medal at the World Indoor Championships in Budapest, Hungary.

In the 800 m at the 2004 Summer Olympics in Athens, Greece, where Jo accompanied teammate and eventual gold medalist Kelly Holmes, she progressed through the first round but in the third of three semi-finals found the pace too fast and finished fifth therefore not qualifying for the final.