Surrey will take on Middlesex at the Kia Oval, while last season's County Champions Essex face Kent at Chelmsford, in the first round of matches in the newly inaugurated Bob Willis Trophy, which gets underway on August 1 after a four-month delay due to the Covid-19 pandemic.
The ECB's truncated domestic calendar, unveiled on Friday, will also feature a one-off women's 50-over competition, involving the eight new teams in the women's elite domestic structure. The fixtures for that event will be finalised at a later date, alongside details of the Vitality T20 Blast, which gets underway on August 27.
"There has been a strong determination across the game to play men's and women's domestic cricket his summer and the fact that we will owes to the significant work and collaboration across the county network," Tom Harrison, the ECB chief executive, said.
"The efforts to deliver a new one-off men's and women's competition, in addition to a shortened Vitality Blast, to meet the unprecedented requirements of playing professional cricket during a pandemic have been remarkable."
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Surrey's meeting with Middlesex will be a restaging of next week's two-day friendly at the same venue, a match which is being used to trial the return of crowds to sporting events as the UK continues to emerge from lockdown.
However, for the time being, all 18 counties will play behind closed doors in the Bob Willis Trophy, for which the teams have been split into three groups of six counties - North, Central and South - with five group-stage fixtures scheduled before a five-day final at Lord's in September.
The competition was named in honour of Willis, the former England captain and fast bowler, who died in December aged 70. The idea was proposed by his friend and former team-mate, Ian Botham, who is also the chairman of Durham.
"As a player there was no better person to turn to in a crisis and as a man there was no one more capable to make you smile and realise the beauty in life," Botham said. "He was an ardent advocate for the longest form of the game and, at a time when all of his great virtues have been needed by us all, I can think of no better person to name this tournament after."
All domestic competitions will be staged under strict health-and-safety protocols, with the ECB agreeing to a range of changes to the playing conditions to help ensure the wellbeing of players, most significantly fast bowlers, who are likely to be the most affected after the lengthy furloughing of many county playing staff.
These have been made in collaboration with the first-class counties and the Professional Cricketers' Association following extensive medical research, and include:
A reduction from a minimum of 96 overs to a minimum of 90 overs in a day's play.
Each county's first innings of a match can last no longer than 120 overs
The follow-on will increase from 150 to 200 runs
The new ball will be available after 90 overs rather than 80 overs
Andrew Strauss, chairman of the Performance Cricket Committee, said: "For all fans of the county game, it is fantastic news that domestic cricket will get underway at the start of August.
"It goes without saying that everyone wants to see competitive red- and white-ball cricket but in these unprecedented times it is crucially important that we recognise that the fitness and wellbeing of players is the top priority after a long lay-off period.
"Following appropriate medical consideration these measures have been put in place for the Bob Willis Trophy to help to protect players from the risk of long-term injury and any impact that could have on their careers."
To help mitigate the possible impact of bad weather on a shortened competition, points awarded for a draw will be increased from five (in the County Championship) to eight. All other points scoring will remain the same as in the County Championship. In the event of a drawn final, the trophy will be awarded to the team that leads on first innings.
"We will need to remain agile to the challenges that will await us during the shortened domestic season," added Harrison, "with the health and wellbeing of our players, staff, officials and fans continuing to be our first priority."
Bob Willis Trophy groups:
North Group Derbyshire, Durham, Lancashire, Leicestershire, Nottinghamshire, Yorkshire
Central Group Glamorgan, Gloucestershire, Northamptonshire, Somerset, Warwickshire, Worcestershire
South Group Essex, Kent, Hampshire, Middlesex, Surrey, Sussex