Big name candidates include Labour former deputy prime minister John Prescott at Humberside, the party's ex-Solicitor General Vera Baird at Northumbria and former Welsh first minister Alun Michael in South Wales.
Other Labour former ministers listed are Jane Kennedy (Merseyside), Tony Lloyd (Greater Manchester), Paddy Tipping (Nottinghamshire) and James Plaskitt (Warwickshire).
Also standing are Conservative ex-minister Michael Mates (Hampshire).
Former deputy chief constable Labour's Ron Hogg (Durham) and ex-assistant chief constable Tory John Dwyer (Cheshire) have thrown their hats into the ring.
Three areas - Dyfed-Powys, North Yorkshire, Staffordshire - have only two candidates which means the outcome will be known on the first count.