Two goals from skipper Shadi Mohamed and defender Emad Al-Nahhas in each half were enough to give the African champions their 32nd league title in history, to perfectly celebrate their 100 year anniversary.
Ahli have now an unassailable nine-point lead over second-placed Ismaili, who have played one match more, with three matches to go.
Playmaker Mohamed Abou-Treika gave Al-Gaish an early scare when he his free-kick floated over the wall and struck the post after seven minutes.
Emad Meteb failed to end his goal drought in the 15th minute when he went through on goal after being set-up by Hassan Mostafa's short pass but his curling right-footed shot missed the target.
The hosts were awarded a penalty seven minutes later when Walid Aslan apparently brought down Meteb inside the area off-ball. Television replays were inconclusive whether there has been contact.
Penalty-kick specialist Shadi stepped-up to send the keeper the wrong way and smash the ball into the top corner of the net.
Al-Gaish had the first opportunity in the 28th minute after Yassin Abdul-Aal's shot from a tight angle was tipped over the bar by Ahli keeper Essam Al-Hadari.
Hassan Mousa controlled a long ball inside the area but fired poorly wide in the 34th minute, wasting another chance for Al-Gaish.
Mousa should have leveled the score three minutes past the hour mark when he was picked out unmarked by Abdul-Sattar Sabri's low cross but failed to control the ball.
Ahli ensured the win ten minutes from time after Tarek Al-Saied's free-kick was miscleared by a defender into the path of Al-Nahhas at the far post for an easy nod-in.