Lampard has been in charge for just over 18 months, but leaves following five defeats in the last eight games.
It comes just 24 hours after his 3-1 win over Luton Town in the FA Cup, but the club’s Premier League form has led to growing concerns.
The 42-year-old achieved a top-four finish last season, which was deemed impressive having taken over when the club were under a transfer ban.
However, this season Chelsea spent £220 million ($275m) on new signings to try and close the gap on Liverpool and Manchester City.
It hasn’t worked, with Timo Werner and Kai Havertz suffering prolonged periods of poor form under their new manager while Chelsea’s performances as a team were increasingly getting worse.
Club chairman Bruce Buck watched on with technical and performance advisor Petr Cech as Leicester City ran out comfortable 2-0 winners against Lampard’s side in their most recent league fixture.
The loss to Brendan Rodgers’ men was just the latest of a series of defeats against the Premier League’s best teams, which recently included reverses against Manchester City and Arsenal.
Chelsea have only beaten West Ham of the top 11 clubs this season, while picking up the second-lowest number of points at this stage of a season since Roman Abramovich bought the club in 2003.
Lampard earned 1.67 points per match in the league, which is the lowest of any manager appointed since Abramovich bought Chelsea.
Former PSG and Borussia Dortmund boss Tuchel is the man to come in to Stamford Bridge, following his sacking by the Ligue 1 champions just before Christmas.
Tuchel, who has been angling himself for the role, could be the right man to get the most out of both Werner and Havertz, as well as Christian Pulisic who was brought through Dortmund’s academy.
Meanwhile, Lampard’s legendary status remains intact and many Chelsea fans would have been happy to see him continue. A display had been planned for the Shed End part of the stadium, urging Chelsea to stick with their all-time record scorer, with 211 goals, and manager.
Lampard previously managed Derby County after retiring from a glorious playing career that saw him win the Champions League and three Premier League titles.