Williams arrives as Davison leaves
The former Blackburn Rovers trainee was one of four players to be released by Pools in May.
The Welshman, who was once a target of Championship side Cardiff City, will aim to impress Mariners boss Russell Slade with his abilities in pre-season training.
The arrival of Williams comes as the club have terminated the contract of fellow goalkeeper Aidan Davison following talks with Grimsby chairman Peter Furneaux.
Three French trialists have also arrived at Blundell Park for pre-season training, as they look to impress Slade.
Cannes star Gilles Noto and the Nice duo of defender Denis D'Amico and striker Jean-Gabin Moubeke will train with the rest of the squad when they return for pre-season training on Monday.
Meanwhile, Hartlepool striker Paul Robinson is set for a move to Conference club York City after turning down a six-month contract with the Victoria Park outfit.
The former Darlington and Newcastle United hit-man rejected the offer to move north of the border to Scottish First Division side Queen of the South this summer.
One player that is staying with Hartlepool for next season is midfielder Darrell Clarke, who has signed a new contract with the North East club after a solid season last term.
