After a run of five successive Premier League defeats without scoring, Rosenior has lost his job 106 days into the 6½-year contract he was handed by Chelsea.
Rosenior took over in January on a deal until June 2032 but leaves fewer than four months later.
Tuesday's defeat at Brighton & Hove Albion made it five straight league losses without a goal scored, which last happened to Chelsea in 1912.
Following the game Rosenior heavily criticised himself, the players and their performance in post-match interviews, while the Chelsea hierarchy spent Wednesday considering his future.
They are likely to have been deliberating who would give the club the best chance of winning Sunday’s FA Cup semi-final against Leeds United and then earning qualification for next season’s Champions League.
Rosenior won each of his first four Premier League games at the helm but a 2-2 draw at home to Leeds United on February 10 started a run of nine league matches which brought just one victory and five points.
That run of form has seen Chelsea drop to seventh in the Premier League — seven points off a top-five spot and guaranteed Champions League qualification — and just three points above 12th-place Fulham.
A conservative system played into Brighton's hands and left the head coach under even more pressure
Rosenior also oversaw an 8-2 aggregate defeat against Paris Saint-Germain in the Champions League last-16, and lost in both legs against Arsenal in the Carabao Cup semi-finals.
Chelsea have yet to beat a Premier League team in their run to the FA Cup semi-finals. After facing Leeds on Sunday, Chelsea are next in league action at home to Nottingham Forest on May 4, before finishing their campaign against Liverpool, Tottenham Hotspur and Sunderland.