Areola, who spent the 2019-2020 campaign on loan at Real Madrid, was at Fulham last season but could not help prevent Scott Parker's team dropping down to the Championship.
The 28-year-old was nevertheless impressive during the campaign and West Ham have moved to keep him in the Premier League for at least another season.
Areola, who was part of France's 2018 FIFA World Cup squad but did not make an appearance in Russia for Les Bleus, has signed a one-year loan deal, which also sees the Hammers have the option to make the transfer permanent in 2022.
Lukasz Fabianski made 35 appearances as David Moyes' team went on to secure European football with a sixth-place finish, though Areola will now provide stern competition to the Poland international.
"Alphonse is an experienced and talented goalkeeper who has played at the highest level and performed very well in the Premier League last season," Moyes said.
"As we prepare for a very busy schedule, he will provide fantastic competition for the goalkeepers already at the football club and we are going to need to use our squad to ensure compete to the best of our abilities across all competitions."
In 36 Premier League appearances last season, Areola conceded 48 goals, outperforming an expected goals against tally of 50.2, suggesting he pulled off saves which he would not have been expected to make.
Only Sam Johnstone, Aaron Ramsdale, Emiliano Martinez and Illan Meslier were forced into action more times than Areola, who made 116 saves in total and also tallied up 39 clearances (including punches), the fifth-most of any goalkeeper in the top flight.
His save percentage of 70.37 ranks him sixth out of goalkeepers to played at least 30 games, while he kept nine clean sheets – as many as Manchester United's David de Gea, though one fewer than Fabianski and 10 less than league-leader Ederson, who was of course helped by a stingy Manchester City defence.
One area where Areola presents an improvement is with his passing, his accuracy of 68.74 per cent some way better than Fabianski (54.91).
"For me it was the best opportunity to sign for this club, to sign for West Ham and to try my best to help the team," Areola said.
"We have really good squad. I watched games last season so I know the potential and the talent in this squad, so I can't wait to start."