The 20-year-old spent last season on loan at Dorchester but he failed to make any first-team appearances during his time at The Avenue Stadium.
Latham is happy with the move and said: “I’m really pleased to be here. It’s great to get this loan deal sorted and I’m buzzing to get started.
“It’s a really good set of lads, a good mix and I’ve really enjoyed getting to know everyone.”
The news follows Jack Rose completing his loan move to League Two outfit Walsall yesterday, and they may not be the only shot-stoppers leaving St Mary’s this summer.
Last week Sky Sports reported the club are willing to listen to offers for senior keepers Fraser Forster and Alex McCarthy.
They claimed Ralph Hasenhuttl is looking to sell players to raise money for transfer funds and gain extra flexibility in the wage structure.
If both players are sold that would leave Angus Gunn as the only recognised senior keeper at the club. Therefore, that could signal that the Saints boss has intentions of bringing in a keeper.
If that does happen, it remains to be seen whether the Austrian will bring in a new number one or a player to be Gunn’s understudy.