|Guinness Pro12 play-offs: Leinster v Scarlets|
|Leinster (10) 15|
|Tries: Ringrose, Conan Con: Nacewa Pen: Nacewa|
|Scarlets (21) 27|
|Tries: S Evans, Shingler, G Davies Cons: Patchell 3 Pen: L Williams 2|
Scarlets produced a superb performance to beat Leinster in the Pro12 semi-final despite having winger Steffan Evans sent off before half-time.
Evans was red-carded for a tip tackle on Garry Ringrose in the 38th minute when Scarlets were leading 21-10.
Evans, back-row Aaron Shingler and scrum-half Gareth Davies scored fine tries for the visitors.
Centre Ringrose and number eight Jack Conan touched down for Leinster who miss out on the 27 May final in Dublin.
Munster host Ospreys in the other semi-final at 18:15 BST on Saturday.
The against-the-odds triumph by Scarlets at the RDS was the first time an away team had won in the Pro12 semi-finals.
Ospreys were the last Welsh club to win the competition in 2012.
The dismissal of Evans could result in the 22-year-old missing out on his first Wales cap as a suspension could rule him out of his country's June Tests against Tonga and Samoa.
Ringrose landed on his head and neck after having his legs lifted by Evans. The red card was shown following several video re-runs of the incident.
Evans watched from the sidelines as Scarlets brilliantly withheld Leinster's response after the interval.
Scarlets had started superbly, scoring first when Evans broke through on the right in the ninth minute.
Isa Nacewa's penalty got Leinster off the mark and then Ringrose burst in for a 24th-minute converted try which put the Irish side 10-7 up.
However, Leinster looked rattled when Scarlets touched down in the 26th and 30th minutes through Shingler and Davies.
Scarlets led 21-10 at the interval, but faced the prospect of playing the entire second half a man down.
They actually outscored their opponents in the second half as lacklustre Leinster could only manage a try by number eight Conan in the 64th minute.
Nacewa somehow missed the straightforward conversion, leaving the hosts 21-15 in arrears.
Scarlets sealed victory with two penalties by Liam Williams after the winger successfully took over from regular kicker Rhys Patchell who had been replaced.
Leinster: Joey Carbery; Adam Byrne, Garry Ringrose, Robbie Henshaw, Isa Nacewa (capt); Johnny Sexton, Luke McGrath; Jack McGrath, James Tracy, Tadhg Furlong, Ross Molony, Hayden Triggs, Rhys Ruddock, Josh van der Flier, Jack Conan.
Replacements: Kirchner for G Ringrose (74), Strauss for Tracy (71), Bent for Furlong (61), Toner for Triggs (51), Leavy for Ruddock (46), Gibson-Park for L McGrath (22), Healy for J McGrath (9)
Not used: R Byrne.
Scarlets: Johnny Mcnicholl; Liam Williams, Jonathan Davies, Scott Williams, Steff Evans; Rhys Patchell, Gareth Daviess; Rob Evans, Ryan Elias, Samson Lee, Lewis Rawlins, Tadhg Beirne, Aaron Shingler, James Davies, John Barclay (capt).
Replacements: Parkes for Patchell (61), J Evans for G Davies (51), W Jones for R Evans (56), E Phillips for Elias (71), Kruger for Lee (65), Bulbring for Rawlins (65), van der Merwe for J Davies (80), Boyde for Barclay (63).
Referee: Marius Mitrea (FIR)