After completing his medical in Dubai, the 24-year-old has put pen to paper on a three-year contract until 2026 and moves to the Middle East in a deal worth a reported £25m.
Jota becomes Al-Ittihad's third marquee signing of the summer transfer window after the arrivals of French duo Karim Benzema and N'Golo Kante on free transfers and will work under the management of compatriot Nuno Espirito Santo.
The Portugal Under-21 international also follows in the footsteps of countryman Ruben Neves in moving to Saudi Arabia, after the latter completed a £47m switch from Wolverhampton Wanderers to Al-Hilal last month.
Jota will now link up will his new Al-Ittihad teammates ahead of their pre-season tour which begins on July 10.
A statement on Celtic's official website read: "After two seasons with the club, one on loan from Benfica and one on a full contract, Portuguese winger, Jota has left Celtic to join Saudi Arabian club, Al-Ittihad.
"In his time in the Hoops, Jota won two league titles as well as picking up winner's medals in both the Scottish and League Cups.
"Everyone at Celtic Football Club wishes Jota success in his future career."
Celtic have made a significant profit from the sale of Jota, who joined the Hoops from Benfica on a permanent basis for around £6.5m last summer following a successful loan spell.
However, Benfica are due a 30% cut of the profit after inserting a future sell-on clause in the player's deal to move to Celtic.
Jota quickly established himself as a key player for Celtic and was named in the 2021-22 PFA Scotland Team of the Year after helping the Hoops with the Premiership title and Scottish League Cup - scoring 11 goals and registering 11 assists in 31 games across the two competitions.
The winger then played a starring role in Ange Postecoglou's treble-winning side last season, contributing with 15 goals and 12 assists in 43 appearances in all tournaments.
Celtic have seemingly already recruited a replacement for Jota after confirming the arrival of Australian winger Marco Tilio from Melbourne City last Friday.
Brendan Rodgers's side are also believed to be considering a summer swoop for Gangwon FC winger Yang Hyun-jun, with both clubs allegedly in discussions over a possible deal worth in the region of £2.1m.