"The Bull's Hour" ( , "Chas Byká") is a social science fiction novel written by Soviet author and paleontologist Ivan Yefremov in 1968. Six months after its publication in book form in 1970 Soviet authorities attempted to remove it from libraries and bookshops after realizing that it contained a sharp criticism of the current state of affairs in the USSR disguised as a critique of "Capitalism" and Chinese-style communism of that time. It was published again in the 1980s "perestrojka" and thereafter.