Koulibaly's move follows the footsteps of his Chelsea teammate N'Golo Kante, who has agreed to join Saudi champions Al-Ittihad.
Kalidou Koulibaly has completed a move to Al-Hilal in Saudi Arabia from Chelsea, becoming the latest player from the English club to make the switch to the Saudi Pro League.
The exact fee for the transfer remains undisclosed. The 32-year-old centre-back joins Ruben Neves, who recently made a £47 million move to Al-Hilal from Wolves.
Koulibaly's move follows in the footsteps of his Chelsea teammate N'Golo Kante, who has agreed to join Saudi champions Al-Ittihad.
Additionally, Edouard Mendy, another Chelsea player, is said to be close to joining Al-Ahli.
The Saudi Arabian league has been attracting notable names from Europe, including Cristiano Ronaldo's move from Manchester United to Al-Nassr earlier this year, and Karim Benzema's transfer from Real Madrid to Al-Ittihad.
Koulibaly arrived at Chelsea last July from Napoli on a four-year deal, bringing with him a wealth of European and international experience.
He played a crucial role in Napoli's victory in the Italian Cup in 2020 and Senegal's triumph in the Africa Cup of Nations in 2022.
However, his time at Stamford Bridge was limited, making just 32 appearances across all competitions and scoring two goals in 23 Premier League matches.
Taking to Twitter, Koulibaly expressed his gratitude and said, "From my first game to my last, it was an honor to wear this badge.”
“Last season wasn't the one we wanted, but I want to thank the fans and everyone at the club for your support."
While the transfer fee for Koulibaly has not been officially disclosed by Chelsea, reports suggest it could be around £20 million.
This influx of European players to the Saudi Pro League aligns with the league's ambition to establish itself among the top five leagues globally.
In June, Saudi Arabia's Public Investment Fund (PIF), which also owns Newcastle United, took over four leading clubs in the country, further solidifying their aspirations.
Although there is uncertainty regarding PIF's stake in Chelsea's ultimate owners, Clearlake Capital, club sources have denied any direct involvement.
Nevertheless, Chelsea could potentially see four of its players join the Saudi Pro League by the end of the summer, with Hakim Ziyech, the Moroccan winger, also being linked with a move.
These departures form part of a larger squad reshaping process at Stamford Bridge under new manager Mauricio Pochettino. As players depart, the club has also been active in acquiring new talent.
Germany forward Kai Havertz is set to join Arsenal in a £65 million deal, and Manchester City's bid of £30 million for Croatia midfielder Mateo Kovacic has been accepted.
Additionally, France forward Christopher Nkunku has arrived from RB Leipzig, and it is reported that Villarreal's Senegalese striker, Nicolas Jackson, will undergo a medical in London ahead of a potential move this weekend.