Gregory David Massialas (born May 20, 1956) is an American foil fencer and fencing coach.

[1] He was one of 461 athletes to receive a Congressional Gold Medal the same year.

[3] He is the founder and head coach of the Massialas Foundation (MTEAM), a fencing club in San Francisco.

Since 2012 he is the national coach of the United States senior foil team, which includes his own son Alexander.

Massialas' daughter Sabrina, now a senior, is also a high-level foil fencer.