Tiernan O'Halloran's late 60th minute try helped Connacht prevail over Glasgow with a 14-7 win to secure a home Pro12 semi-final at a rain-hit Sportsground.
The two sides will clash once again in a couple of weeks' time as Pat Lam's men will be hoping to repeat the outcome to reach their first ever Pro12 final after what has proven to be their 'best ever season'.
Bundee Aki scored the opening try for Connacht in the 19th minute as fly-half Alan MacGinty successfully scored the conversion.
Connacht valiantly defended their seven-point advantage entering the half-time break.
Prop Gordon Reid brought back Warriors with a try as he managed to crash over off the back of a close-in ruck. Finn Russell added the extras as the scorecard reflected 7-7 by the end of 48th minute.
Warriors were reduced to 14 men for the rest of the match as Prop Sila Puafisi was sent off by referee Ian Davies for leading with the head on Marmion at a ruck.
Connacht full-back O'Halloran outsmarted his opposite number Stuart Hogg to collect O'Leary's cross-field kick and score the decisive try on the 60th minute. Shane O'Leary successfully made the conversion as Connacht got a vital seven-point lead with 19 minutes remaining for the final whistle.
Glasgow had a closing opportunity to get back in the game with five minutes remaining on the clock, however, Connacht forced another error and a final ruck penalty was ample to cruise them safely home.