Marcellus Vernon Wiley, nicknamed "Dat Dude" (born November 30, 1974 in Compton, California) is a retired American football defensive end who played 10 seasons in the NFL for four different teams. He was selected with the 22nd pick of the second round of the 1997 NFL Draft out of Columbia University by the Buffalo Bills. After four seasons with the Bills, he played for the San Diego Chargers, Dallas Cowboys and Jacksonville Jaguars. He was selected to the AFC Pro Bowl team in 2001, as a member of the San Diego Chargers.
At Saint Monica Catholic High School in Santa Monica, California, Wiley starred in both football and track and field. In football, he was an All-Conference pick. Wiley was a teammate of Adrian Klemm.
At Columbia University, Wiley played both tailback, defensive end, and kick returner for the Lions. He was a first team All-American, and All-Ivy League pick.