Leinster are bidding to become only the second team ever to win back-to-back European titles, after Leicester in 2001 and 2002, and the first to claim three crowns in four seasons.
But standing opposite them in Bordeaux will be Clermont Auvergne, the French standard-bearers, the coming force in European rugby and the last team to beat Leinster in the Heineken Cup.
It is a clash worthy of the final itself and Sexton rates Leinster's challenge as greater than any they have ever faced on the European stage.
Greater than their final victories over Leicester in 2009 and Northampton last year, when Sexton inspired their sensational comeback from 22-6 down to a 33-22 victory.
Greater than either of their semi-final triumphs - including the win against Munster in 2009, when Leinster produced one of the great European performances - or the defeat at the same stage to Toulouse in 2010.
"We know this will be the toughest test we have ever faced," Sexton said.
"Toulouse a couple of years ago was tough, we think this is going to be even tougher.
"They have such a good squad. Our coach (Joe Schmidt) knows how good they are. It is going to be a really big battle. It is not easy going to France and getting a win.
"We are thinking of it as our final because it's our next game. There is a lot of nervousness but everyone is pretty excited as well.
"We have to play our best to get a result."
Schmidt knows Clermont's qualities because he helped coach them to the French Top 14 title before moving to Leinster.
But any advantage of inside information is bound to be cancelled out by the presence of Nathan Hines in the Clermont second row, 11 months after he helped Leinster win the Heineken Cup.
"He is still a mate although we are putting that on hold for the week," Sexton said.
"We know the type of threat he is going to bring, he gave this club so much in the years he was here. We want to beat him this weekend."
Hines was replaced in the Leinster second row by New Zealand World Cup-winner Brad Thorn and their battle in Bordeaux tomorrow will be one of many mouthwatering head-to-head contests.
Aurelien Rougerie and Wesley Fofana, the first choice French midfield, will face off against Brian O'Driscoll and Gordon D'Arcy.
The Clermont back three of full-back Lee Byrne, Julien Malzieu and Sitiveni Sivivatu will be in direct opposition to Leinster's Rob Kearney, Luke Fitzgerald and Ica Nacewa.
Sexton starts opposite Brock James, who masterminded Clermont's quarter-final victory over Saracens in which the giant bearded Georgian prop Davit Zirakashvili was a major influence.
While Clermont sent out a strong message of intent at Vicarage Road, Leinster displayed their awesome attacking prowess in dispatching the Cardiff Blues to reach a fourth consecutive semi-final.
"Clermont want to be a big European club, to be a part of Heineken Cup history," said scrum-half Morgan Parra.
"Leinster usually always perform well in these kind of big fixtures. They are used to it, but for us it is all new."
Parra admitted nerves had affected Clermont's preparations ahead of their first ever Heineken Cup semi-final.
"On Wednesday we had a contact session which we usually love but this time it was like everybody was scared. It was catastrophic. It looked awful," he said.
"We must really focus at the beginning on the game in particular because Leinster are very dangerous during the opening stages. And then we must stay calm.
"It's vital that we don't do stupid things just because of the excitement."
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The entire All Blacks apparel line has been updated for 2013/14. Check out the New Zealand All Blacks polo.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Gilbert Blitz 8S rugby cleat is a great cleat at a great price of $69.99. Get a new pair of cleats today.
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
The All Blacks Performance t-shirt is black with hints of blue from the training jersey. Very Cool.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.