Northampton will have a home Heineken Cup semi-final after pulling off a shock defeat of last year's beaten finalists Biarritz in a tight game in San Sebastian.
The Basque side led 3-0 at half time and doubled that lead with a second Dimitri Yashvili penalty but Northampton struck back with a Robbie Kydd interception try, converted by Carlos Spenser, and they held out to win 6-7.
Northampton, who lost home and away to the same opposition in the group stages and had been given no chance of success today, will now play London Wasps at the Ricoh Arena in Coventry.
Wasps delivered a 35-13 thumping to a Brian O'Driscoll-less Leinster at home in Adams Park yesterday evening, ending any Irish hopes of lifting the title this year.
Defending champions Munster were knocked out on Friday night by the Llanelli Scarlets in Stradey Park.