Fly-half Stephen Myler kicked 20 points for Northampton as they secured a home semi-final in the European Challenge Cup with a 42-13 victory.
Opponents Connacht had three players sin-binned, and Saints, who have won 32 of their last 33 games at Franklin's Gardens, will play the winners of tomorrow's quarter-final between Saracens and Newcastle on the first weekend in May.
Myler landed six penalties from six attempts to punish Connacht's malfunctioning scrum who repeatedly fell foul of French referee Romain Poite.
The visitors, who were watched from the stand by Ireland's Grand Slam-winning coach Declan Kidney, could not handle the strength of the Saints pack at the set-piece but were competitive until caving in after full-back Gavin Duffy received their third yellow card.
Saints cashed in with four tries in the final 11 minutes from Neil Best, Joe Ansbro, skipper Bruce Reihana and Chris Mayor, with Myler and his late replacement Barry Everitt converting one each.
Connacht replied with an excellent try from number eight Ray Ofisa, and kicking points from fly-half Ian Keatley, but they were overwhelmed by the loss of Brian McGovern, Jonny O'Connor and Duffy to the sin bin.
Peter O'Mahony was named man of the match against England last month
21 April 2017, 7:22pm
Peter O'Mahony's performance in the RBS 6 Nations finale for Ireland against England was crucial to his selection for the British & Irish Lions on Wednesday, Ireland and Lions defence coach Andy Farrell has revealed.