In a change to previous County Championships, the 2021 competition will see the 18 first-class counties split into three groups, with Middlesex in Group 2, along with Gloucestershire, Hampshire, Leicestershire, Somerset and Surrey.
Middlesex will entertain Somerset at Lord’s from Thursday 8 April, before Surrey are the visitors later in the month, from 22 April.
Stuart Law’s side will then welcome Gloucestershire on 6 May, and Hampshire a week later, from 13 May.
Each team will play ten matches in the group stages, with the top two counties in each group progressing to Division One for the second stage of the County Championship, later in the summer.
The other 12 counties will move into Divisions Two and Three. The third and fourth-placed teams will progress to Division Two while the fifth and sixth-placed teams move to Division Three.
All counties will then play a further four matches later in the season, which will determine their final place in the County Championship. The title will be won by the team that finishes top of Division One.
The top two teams in Division One will play for the Bob Willis Trophy in a five-day final to ensure a showpiece event concludes the first-class domestic season.
The 2020 competition, played for the first time, saw the final held at Lord’s and 2019 County Championship winners Essex reaffirmed their position as the premier red-ball side in the country, as a draw against Somerset was enough to see them lift the trophy.
The four initial County Championship fixtures at Lord’s are added to the two provisional international matches that have been announced for the Home of Cricket, with England’s Men taking on Pakistan in a One-Day International on Saturday 10 July, and India in a Test Match between 12 and 16 August.
Further fixtures for the Ground will follow in the early part of 2021.
Middlesex v Somerset, Thursday 8 April - Sunday 11 April
Middlesex v Surrey, Thursday 22 April - Sunday 25 April
Middlesex v Gloucestershire, 6 May - Sunday 9 May
Middlesex v Hampshire, 13 May - Sunday 16 May