Al-Ittihad confirmed the signing on social media, with the 35-year-old putting pen to paper on a deal covering this season and including an option for a further year, according to reports from journalist Ben Jacobs relayed by Fotbollstransfers.
The move ends a period as a free agent for the veteran midfielder, who had been without a club since his Al-Ettifaq deal expired at the end of last season.
The Dutch midfielder played a key role in Liverpool's 2018/19 Champions League triumph, making 237 appearances for the Merseyside club between 2016 and 2021, before leaving as a free agent for Paris Saint-Germain.
He made just 31 appearances in two seasons in France, scoring once, and struggled to establish himself as a regular starter before spending the 2022/23 campaign on loan at Roma. He made his move to Saudi Arabia permanent in September 2023, joining Al-Ettifaq under then-manager Steven Gerrard.
Wijnaldum scored 17 goals and added six assists in 34 matches for Al-Ettifaq last season, but his contract expired this summer and he had been linked with a return to the Premier League with Chelsea before Al-Ittihad moved to secure his signature as a free agent, avoiding the need to negotiate a fee with his former club.
He joins a squad that has also lost Fábio Henrique Tavares, known throughout his career as Fabinho, this summer following the Brazilian's contract expiry, and arrives alongside fellow new signings Rakan Kaabi, from Al-Fayha, and Dion Lopy, from Spanish side Almería, as Al-Ittihad moved to strengthen their midfield options before the Saudi window closed.
Earlier in his career, Wijnaldum came through the ranks at Feyenoord before spells with PSV and Newcastle United, moving to Merseyside in 2016. Capped 96 times by the Netherlands, he has scored 28 goals for his country and was part of the squad that finished third at the 2014 World Cup and runners-up at the 2018/19 UEFA Nations League.
He captained Al-Ettifaq during his three seasons in Saudi Arabia and will now aim to bring that experience and leadership to an Al-Ittihad squad chasing domestic and continental honours this season.