Per the AP, teams seeded ninth or lower that have advanced to the Final Four since 1979, when the NCAA began seeding all teams:
1979 — No. 9 Pennsylvania: lost to Michigan State in semifinals, lost to DePaul in third-place game
1986 — No. 11 LSU: lost to Louisville in semifinals
2006 — No. 11 George Mason: lost to Florida in semifinals
2011 — No. 11 Virginia Commonwealth: lost to Butler in semifinals.