The 57-year-old Spaniard had been out of work since leaving Wolves on the eve of the just-concluded Premier League season.
Lopetegui will officially begin work with the Hammers on July 1, replacing David Moyes after the Scot’s exit at the end of this season.
“We came here with the idea and the thought to make a big, big noise,” Lopetegui said. “That’s why we came here, and we are excited by this challenge.
“Of course, we are going to do our best to help the club and the team to achieve the best level and to achieve our aims.
“I assure the fans that they are going to be key in all our achievements.”
West Ham joint-chairman David Sullivan said Lopetegui’s appointment would “ensure a strong opportunity to build on the positive progress made in recent seasons”.
Lopetegui led Sevilla to Europa League glory in 2020, a success that restored his reputation after he was sacked by Real Madrid in 2018.
He had been dismissed by Spain just before the start of the 2018 World Cup after it was announced he would quit to take charge of Real following the tournament.
However, the former goalkeeper’s brief spell at the Bernabeu was a dismal failure as he lasted just 14 matches before being axed after a humiliating 5-1 loss against Barcelona.
He moved to Wolves in November 2022 when the Molineux outfit were bottom of the Premier League.
After impressively guiding them away from relegation danger to a 13th-place finish, Lopetegui became frustrated by the club’s financial situation and left by mutual consent in August 2023.
West Ham technical director Tim Steidten said: “He was a stand-out candidate to become our head coach and I am personally delighted that we have chosen to work together.”
Moyes had led West Ham to their first major trophy in 43 years when they won the Europa Conference League in 2023.
But the Hammers finished ninth in the Premier League in the 2023/24 season, missing out on European qualification.
Former Manchester United boss Moyes, who had been in charge since 2019, fell out of favour among fans due to his cautious tactics.
Lopetegui plans to improve on Moyes’ achievements as he looks to make his mark in east London.
“We will try to put our stamp on the club. I feel that we have a fantastic platform,” he said.
“I think the last few years have been very good to have this base, but my ambition as a coach is always to be better, to achieve more and bigger aims. We are very ambitious about this.”
© Agence France-Presse
Photo: Twitter @TayWH5