Provided is a molybdenum sulfide that is ribbon-shaped and particularly suitable for a hydrogen generation catalyst. Disclosed are a ribbon-shaped molybdenum sulfide, in which 50 particles as measured by observation with a scanning electron microscope (SEM) have a shape of, on average, 500 to 10000 nm in length, 10 to 1000 nm in width, and 3 to 200 nm in thickness; a method for producing the ribbon-shaped molybdenum sulfide, including: (1) heating a molybdenum oxide at a temperature of 200 to 1000° C. in the presence of a sulfur source; or (2) heating a molybdenum oxide at a temperature of 100 to 800° C. in the absence of a sulfur source, and then heating the molybdenum oxide at a temperature of 200 to 1000° C. in the presence of a sulfur source; and a hydrogen generation catalyst including the ribbon-shaped molybdenum sulfide.