Leinster's winning run came to an agonising end on Saturday (AEDT) as it was beaten by a late Mark Bennett try in a 29-24 Pro14 defeat to Edinburgh.
Last season's semi-finalist had not lost in any competition since its previous trip to Scotland in November, racking up nine consecutive wins since that defeat to Glasgow Warriors.
The Irish province led 19-17 at half-time after tries from Max Deegan, Scott Fardy and Barry Daly, whose second try of the match sent Leinster 24-22 in front with 16 minutes left to play.
However, Bennett — on the end of a Jaco van der Walt chip that was touched down by Glenn Bryce — crossed with two minutes remaining and Sam Hidalgo-Clyne converted to put the match beyond Leinster, which goes level on points with Conference B leader Scarlets thanks to its two bonus points.
Ulster is now eight points adrift of the top two after it subjected a sorry Southern Kings outfit to another thumping defeat at the Kingspan Stadium, a match that saw Joy Neville become the first woman to referee a Pro14 fixture.
The hosts racked up nine tries in a 59-10 demolition, although the seventh came at a cost, with Rob Lyttle left writhing in agony with a hamstring injury after running the length of the pitch.
The Dragons missed out on a first Pro14 win since September as they were held to a 15-15 draw by Conference A leader Glasgow Warriors, while Connacht beat the Ospreys 26-15 after back-to-back defeats.