Makuuchi (幕内^?) or makunouchi (幕の内^?) is the top division of professional sumo. Its size is fixed at 42 wrestlers (rikishi), ordered into five ranks according to their ability as defined by their performance in previous tournaments.

This is the only division that is featured on NHK's standard live coverage of sumo tournaments. The lower divisions are shown on their satellite coverage, with only makuuchi broadcast having bilingual commentary.

Makuuchi literally means "inside the curtain", a reference to the early period of professional sumo, when there was a curtained-off area reserved for the top ranked wrestlers to sit prior to appearing for their bouts.

Wrestlers are considered for promotion or demotion in rank prior to each grand tournament according to their performance in the one previous. Generally, a greater number of wins than losses (kachikoshi) results in a promotion, and the reverse (makekoshi) results in demotion. There are stricter criteria for promotion to the top two ranks, which are also privileged when considered for demotion.