Mitrovic was desperate to make the move happen and he will join the likes of Neymar, Ruben Neves, Kalidou Koulibaly, Yassine Bounou, Malcom and compatriot Sergej Milinkovic-Savic as Hilal's marquee signings this summer.
Mitrovic's 14 league goals last season helped Fulham finished 10th although he was banned for eight games for pushing a referee.
The 28-year-old joined Fulham initially on loan from Newcastle United in 2018 and scored 111 goals in 205 appearances.
A Fulham statement on Saturday evening read: "The club can confirm that Aleksandar Mitrović has this evening left to join Al Hilal in the Saudi Pro League for a club-record transfer fee.
"The club had reluctantly accepted a revised offer as the player had consistently made his desire to leave known.
"Mitrović joined Fulham in January 2018, initially on a loan deal before signing permanently that summer. In his first season, he helped the Whites to a Championship Play-Off Final win, securing promotion to the Premier League, the first of his three promotions to the top division.
"During the club's 2021/22 Championship title-winning campaign, he scored 43 times to set the record for most goals scored in a 46-game English league season, and equal a club record for most goals scored in one campaign.
"We wish Aleksandar all the best in this next step in his career."
Fulham have won one and lost one from their two league games this season.
