Surrey will begin their bid for a fourth successive County Championship title with a tough away game against Essex.
No team has won four in a row since Surrey lifted the trophy in seven successive years from 1952 to 1958.
Last season's runners-up Hampshire will start at home against promoted Yorkshire, while Sussex, who were promoted as champions, will be away to Warwickshire.
The opening round of fixtures in Division Two, which also starts on 4 April, sees relegated Lancashire travel to Lord's to play Middlesex, while Kent begin life back in the second tier with an away game against Northants.
In the One-Day Cup, 2024 winners Glamorgan will play Hampshire at Neath on Tuesday, 5 August, but the 50-over women's competition will begin in April, with the two finals taking place over the weekend of 20-21 September.
The men's final will again be played at Trent Bridge, with the women's showpiece at Utilita Bowl the following day.
The County Championship will follow the same schedule as this year, with eight rounds of Friday to Monday games through April and May, then a break before resuming for two weeks at the end of June, both beginning on Sundays.
Another pair of back-to-back games will follow at the end of July before the red-ball campaign reaches its climax with the final three rounds of games in September.
They will begin on 8, 15 and 24 September, with the last day of the season on Saturday, 27 September, two days earlier than in 2024.
Kookaburra balls will again be used for the Championship games in June and July, with the Dukes ball retained for the early and season-ending rounds.
Sussex will be back in the top flight for the first time since 2015, having finished 20 points clear of Yorkshire at the top of Division Two.
The Tykes - who will have Anthony McGrath in charge as their new head coach, replacing Ottis Gibson - secured their promotion with a run of wins in the second half of the summer.
Essex have yet to confirm a replacement for McGrath, who left them after nine seasons at Chelmsford, while relegated Kent have yet to appoint a successor to departed head coach Matt Walker.
One-Day Cup shake-up
The men's One-Day Cup has again seen a shake-up for the group stage, with Derbyshire, Hampshire and Worcestershire swapping with Sussex, Warwickshire and Yorkshire.
Group A: Notts Outlaws, Essex, Worcestershire, Surrey, Gloucestershire, Glamorgan, Hampshire, Leicestershire Foxes, Derbyshire Falcons.
Group B: Kent Spitfires, Yorkshire, Somerset, Lancashire, Durham, Warwickshire, Northamptonshire Steelbacks, Middlesex, Sussex Sharks.
The winners of each group will advance to the semi-finals, with the teams finishing second and third meeting in a quarter-final for a place in the last four.
As with the T20 Blast, the women's competition will feature separate tournaments for the eight fully professional county teams and a League 2 tier of 10 other sides.
The main competition will see each of the eight teams playing the other seven home and away, with the top four progressing to the semi-finals.
There will be 10 teams in League 2 with nine games for each in the group stage and the top four again advancing to the knockout stage.
Next season sees the women's game move away from regional teams following five seasons of the Rachael Heyhoe Flint Trophy, which was won in 2024 by Sunrisers.
County Championship opening fixtures
All games start on 4 April 2025 (11:00)
Division One
Essex v Surrey
Hampshire v Yorkshire
Nottinghamshire v Durham
Somerset v Worcestershire
Warwickshire v Sussex
Division Two
Derbyshire v Gloucestershire
Glamorgan v Leicestershire
Middlesex v Lancashire
Northamptonshire v Kent
Men's One-Day Cup opening fixtures
Tuesday, 5 August 2025
Chester LS: Durham v Sussex
Neath: Glamorgan v Hampshire
Cheltenham: Gloucestershire v Derbyshire Falcons
Sedbergh: Lancashire v Northamptonshire Steelbacks
Sookholme: Notts Outlaws v Essex
Scarborough Yorkshire v Warwickshire
Wednesday, 5 August
Radlett: Middlesex v Somerset
Guildford: Surrey v Leicestershire Foxes
Women's One-Day Cup opening fixtures
Wednesday, 23 April 2025
Chester LS: Durham v Essex
Beckenham: Surrey v Somerset
Trent Bridge: The Blaze v Lancashire
Edgbaston: Warwickshire v Hampshire