Diane Farrell Wainio (born November 5, 1961) is an American former professional tennis player.

She was raised in Binghamton, New York and played collegiate tennis for the University of San Diego.

Farrell, who reached a career best singles ranking of 220, qualified for the main draw at Wimbledon in 1986.

All three of her wins in qualifying went beyond 6–6 in the third set, against Cláudia Monteiro, Sabina Simmonds and Elisabeth Ekblom.

She won two ITF doubles titles, including a $25,000 tournament in Hopewell.