Leinster halted Toulouse's 12-match unbeaten run to replace them at the top of European Rugby Champions Cup Pool 1, while Ulster and Edinburgh also claimed big Top 14 scalps on Saturday.
Toulouse had not been beaten since September, but Leinster ended their 100 per cent Champions Cup record with a 29-13 bonus-point victory at the RDS Arena on a great day for Pro14 clubs.
Injury-hit defending champions Leinster lost Luke McGrath to a knee problem, but lead Toulouse by three points and will be assured of a home quarter-final if they win at Wasps next weekend.
Toulouse are still on course for the last eight with a home clash against Bath to come given their points tally, but they were brought back down to earth on a windy afternoon in Dublin.
Leinster, missing Johnny Sexton and a whole host of fellow internationals, led 10-6 at the break after Jack Conan ploughed his way over from close range and three second-half tries put them out of sight.
Dave Kearney took a pinpoint cross-field kick from Ross Byrne before finishing superbly, then Sean Cronin and Adam Byrne crossed before Cheslin Kolbe touched down right at the end for a well beaten Toulouse side.
Jacob Stockdale claimed a double as Ulster kept their hopes of securing top spot in Pool 4 alive with a 26-22 defeat of previously unbeaten leaders Racing 92 in a classic battle at Kingspan Stadium.
The prolific Stockdale maintained his record of having scored in every round, the competition's leading scorer chasing onto his own kick for a magnificent solo try in the second half in Belfast.
Simon Zebo's try reduced the deficit to 16-10 at the break and last year's runners-up were only a point behind following tries from Brice Dulin and Olivier Klemenczak, but Will Addison's second penalty completed the scoring as Ulster ground it out.
Edinburgh will head into their decisive Pool 5 clash with Montpellier with a three-point advantage at the summit after downing struggling three-time champions Toulon 28-17 at Stade Mayol.
Richard Cockerill's side rallied from 12-8 down at the interval, Blair Kinghorn and James Johnstone adding to a Darcy Graham try to keep Toulon rooted to the bottom.
Montpellier thrashed Newcastle Falcons 45-8, while Bath edged out Premiership rivals Wasps for their first Pool 1 win courtesy of a late Rhys Priestland penalty and the Scarlets hammered Leicester Tigers 33-10 in Pool 4.