Eustachy replaces Tim Miles, who left the Rams to coach Nebraska on March 23.
Miles led the Rams to the NCAA tournament and a fourth-place finish in the Mountain West (8-6) and a 20-12 overall record in 2011-12. The Rams lost to Murray State in the second round in Louisville.
A decade ago, Eustachy was one of college basketball's hottest commodities after leading Iowa State to consecutive Big 12 regular season championships in 2000 and 2001, heady territory for a program that's traditionally flip-flopped between middling and mediocre.
The fall was swift and severe.
Pictures surfaced in 2003 showing Eustachy partying with college students. He was quickly out of a job and in rehab, then spent a season out of coaching before resurfacing at Southern Miss in 2004. The Golden Eagles made the NCAA tournament this season and lost in the round of 64. It was the school's first tournament appearance since back-to-back appearances in 1990 and '91.