Shelbourne face English Premier League opposition in the penultimate round of the league phase of the UEFA Conference League, while Shamrock Rovers need to bring three points home from Iceland in their bid to qualify for the play-off round.
Here is all you need to know about the games.
TV
Both matches will be live on Premier Sport 1. Shamrock Rovers are on TNT Sports 5, with Shelbourne on TNT Sports 2.
ONLINE
There will be a live blog on RTÉ.ie and the RTÉ News app on the Shelbourne v Palace game.
PRIDE AND POINTS
Shamrock Rovers are up first tonight at 5.45pm. Both Irish teams sit on a single point after four matches but one has the more realistic chance of progress.
The Premier Division champions have their difficult games out of the way. Losses to Sparta Prague, Celje and Shakhtar Donetsk, with an excellent draw away to AEK Athens, leaves them needing two wins to have any chance of making inside the top 24. The final home fixture is against Maltese outfit Hamrun Spartans.
Shels are also in the position of holding one point from four games, but given they have Premier League opposition coming to Dublin and a trip to Slovenia to face Celje, it's not realistic to think they can progress.
BREIDABLIK REVENGE
Shamrock Rovers will count their previous game against the Icelandic side as one they didn’t perform at their usual level.
Now comes a chance for revenge.
Breidablik won both legs in a 2023 Champions League qualifier.
If there is a positive, the Hoops don’t have to return to the venue of the away defeat which came on a tricky astro surface.
Tonight’s clash will be in the Laugardalsvöllur which is a 95% grass pitch. It’s used for Iceland’s international home games and is booked to go under works in the future to removing a running track and expand the 9,500 capacity. It will be cold, as expected, with temperatures just above freezing around kick-off time.
Breidablik have two points accumulated so far, which means they too will be targeting this encounter for a crucial three points in the bid to stay in the competition.
One of their draws came against the side currently top of the Conference League, Samsunspor of Turkey, so they have shown some pedigree.
There are a lot of similarities between the sides. Breidablik are regular qualifiers in Europe and became the first side from their nation to qualify for a European competition outright.
Their squad has a host of experience and they are even more out of season than Shamrock Rovers with the Icelandic league finishing in late October.
You can expect the game to be quite even; they're two well-matched sides.
PALACE MATTERS
For Shels, while in theory they can qualify, it's a daunting task to face the fourth-placed side from the richest league in the world.
The Reds have been unfortunate - and perhaps will take plenty of knowledge from this campaign - having failed to take goalscoring chances and shipped goals to lose by narrow margins.
Their latest result - a 2-0 defeat in Alkmaar - had positives and they will hope to create an upset in their final matches at least.
Crystal Palace have not had things their own way so far in the campaign, losing to AEK Larnaca.
It's a different story in the Premier League with just three losses in 15 matches seeing them sit fourth in the table.
Manager Oliver Glasner has spoken about balancing European commitments and the league.
Tonight's game has become important for the Eagles as they look to try to avoid a play-off and qualify in the top eight.
He will resist temptation to rotate massively in tonight's clash despite with a home match on Sunday against Manchester City.
Instead he will rest players for their final clash with KuPS.
That will make it a lot harder for the Reds.
WHAT THEY SAY
Shels boss Joey O'Brien is keen to see his side show their best when the most eyes are watching. Tonight's clash in Tallaght Stadium is a sellout with over 9,000 in attendance.
"Sometimes you can think too far about things and think of who you're playing against and where they've come from and stuff like that. But for me, that doesn't work. It's about yourself, being proud of your own journey, how you've got here, incredible stories to get to this game.
"There were a lot of positives," O'Brien added of their last clash in Alkmaar.
"I think we started really well in the game. Their first shot on target didn't come until the second-half. So going away from home in Europe and having that was really good. I felt that in possession we didn't show our real quality and how good we are as players, so that is a big thing for me tonight, that the lads embrace the challenge and show how good we are in possession."
Palace manager Oliver Glasner has heard of improvements in the League of Ireland: "It's tricky for them because their season has ended," said Glasner. "They are not in the rhythm anymore.
"They ended the season in third place, but are a very physical team.
"I think they (Irish teams) are doing well and progressing. I’m told many English internationals could also play for Ireland because of their relatives, but they are doing great."
Hoops boss Stephen Bradley said in Iceland: "It's an opposition team we know quite well, although they are in transition with their manager changing recently, they still have some very good players and a lot of those players came up against us a couple of years ago.
"We both have to win. It's a one-off game and I imagine both teams will go to win it. It has the makings to be a really good game."
TEAM NEWS
Danny Mandroiu, Aaron McEneff and John Honohan are out for Shamrock Rovers. Shels will have the same squad as the clash with AZ.
