The 1930–31 Illinois Fighting Illini men's basketball team represented the University of Illinois.

James Craig Ruby was an American college basketball player and coach. A two-time All-American and All-Missouri Valley Conference forward at the University of Missouri, he took over the head coaching position of his alma-mater in 1920. Ruby coached the Tigers for two seasons, compiling a record of 33 wins and only 2 losses. Both of Ruby's Missouri teams were retroactively named national champions by the Premo-Porretta Power Poll. Ruby was subsequently recruited by University of Illinois athletic director George Huff to take over the Fighting Illini’s men's basketball coaching duties.