The reigning Investec Champions Cup champions lifted the trophy for the second consecutive season as they proved too strong for Leinster Rugby at the San Mamés stadium in Bilbao.
Tommy O'Brien got Leinster Rugby off to the perfect start, crossing in the corner after 8 minutes, but Union Bordeaux Bègles proved why they're reigning champions by hitting back five times.
Captain Maxime Lucu was the first to cross for the French with a snipe under the posts, before Pablo Uberti finished out wide to put them in front.
The inevitable Louis Bielle-Biarrey then stepped his way over once, before finishing with aplomb after Damian Penaud grubbered through.
Yoram Moefana was next to touch down after intercepting on the halfway line, putting UBB firmly in the driving seat at the break. Union Bordeaux Bègles led 35-07 at the halftime break.
Leinster fought and fought with Joe McCarthy and Garry Ringrose touching down for the reigning URC champions in the second half.
But two penalties from the boot of Maxime Lucu in the second half were enough to see UBB over the line.
Scorers:
Leinster Rugby: Tries: Tommy O'Brien, Joe McCarthy, Garry Ringrose. Conversions: Harry Byrne, Ciaran Frawley.
Union Bordeaux Bègles: Tries: Maxime Lucu, Pablo Uberti, Louis Bielle-Biarrey (2), Yoram Moefana. Conversions: Maxime Lucu (5). Penalties: Maxime Lucu (2).
Teams
Leinster Rugby: 15 Hugo Keenan, 14 Tommy O’Brien, 13 Garry Ringrose, 12 Robbie Henshaw, 11 Rieko Ioane, 10 Harry Byrne, 9 Jamison Gibson-Park, 8 Caelan Doris (captain), 7 Josh van der Flier, 6 Jack Conan, 5 James Ryan, 4 Joe McCarthy, 3 Tom Clarkson, 2 Dan Sheehan, 1 Andrew Porter. Replacements: 16 Ronan Kelleher, 17 Paddy McCarthy, 18 Tadhg Furlong, 19 Diarmuid Mangan, 20 Max Deegan, 21 Luke McGrath, 22 Ciaran Frawley, 23 Jamie Osborne.
Union Bordeaux Bègles: 15 Salesi Rayasi, 14 Pablo Uberti, 13 Damian Penaud, 12 Yoram Moefana, 11 Louis Bielle-Biarrey, 10 Matthieu Jalibert, 9 Maxime Lucu (captain), 8 Marko Gazzotti, 7 Cameron Woki, 6 Pierre Bochaton, 5 Adam Coleman, 4 Boris Palu, 3 Carlü Sadie, 2 Maxime Lamothe, 1 Jefferson Poirot. Replacements: 16 Gaetan Barlot, 17 Ugo Boniface, 18 Ben Tameifuna, 19 Lachie Swinton, 20 Temo Matiu, 21 Bastien Vergnes-Taillefer, 22 Arthur Retiere, 23 Hugo Reus.