Al Ahli came back from a first-leg deficit to beat Al Ittihad 2-0 win and win 2-1 on aggregate over their cross-Jeddah rivals and book a place in the final of the AFC Champions League for the first time in their history on Wednesday.
Al Ittihad, seeking a third Asian crown in eight years, held a slender one-goal advantage from the first leg nine days ago.
However, goals from Moataz Al Muta and Victor Simoes in front of their own fans mean Al Ahli will travel to South Korea to face Ulsan Hyundai in the final on November 10.
Ulsan had also reached their first ever AFC Champions League final earlier Wednesday in Korea after they weathered an early onslaught to beat Uzbek side Bunyodkor 2-0 for a 5-1 aggregate win.
"I'm really happy with this win and thank God we eventually won today," said Ahli coach Karel Jarolim.
"We had good chances in the first half of the game but we failed to score and we eventually took the lead by the end of the first half.
"We managed not to lose the ball in the second period and we forced Al Ittihad to move without the ball and this affected them physically.
"Of course we tried to create some more chances but we missed the last touch before Victor managed to score."
Al Ahli, backed by a packed house at the Prince Abdullah bin Faisal Stadium, were in the ascendancy right from the whistle and the biggest surprise was that they took so long to open the scoring.
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Simoes hit the woodwork as early as the seventh minute with a vicious left foot shot while five minutes later the Brazilian fired another effort over the bar.
Al Muta caused the Al Ittihad defence a host of problems with his runs from deep and Mabrouk Zaid was called upon to push his 32nd minute header round the post while two minutes later the midfielder's deflected effort was cleared off the line by Osama Al Harbi.
But, with only a minute remaining in the half, Al Ahli finally claimed the goal they deserved when Diego Morales' corner was inadvertently flicked on by Al Ittihad striker Naif Hazazi and Al Muta powered his header home.
The goal for Al Ahli instilled some urgency into an Al Ittihad side that had looked lethargic with Hazazi shooting wide after turning the home defence.
The game looked to be headed for extra time when, with six minutes remaining, Simoes raced onto a long punt forward, outpacing Al Harbi before thumping his left foot shot past Zaid to send the fans wild with joy.
"Unfortunately today we didn't play well in the first half and this probably has cost us the match," said Al Ittihad coach Raul Caneda.
"Our players didn't show what they were supposed to do and what we were looking for.
"We didn't have a good performance in the first half and that's why Al Ahli scored late in the first period. We improved in the second half and we were close to scoring, but we conceded the second goal and this affected us."
Al Ahli will now meet Ulsan with the aim of becoming the first club from Saudi Arabia to win the title since Al Ittihad's second victory seven years ago.
"I want to thank my players and our fans who stood next to us and supported the team throughout the match," said Jarolim.
"Our focus was on this match and hopefully we will now start preparing for the match against Ulsan."