The two surprise finalists were both searching for their first major title, but it was Cilic who dominated from start to finish against Nishikori, who seemed to be feeling the effects of his exhausting run to the final.
Cilic broke three times on the way to taking the first two sets before he came through the third in decisive fashion to record a 6-3 6-3 6-3 triumph.
Read below to see how the action unfolded on the Arthur Ashe Stadium court at Flushing Meadows.
9.34pmIf someone had said to you at the start of the year that Kei Nishikori and Marin Cilic would be contesting the 2014 US Open final, you would have had received a weird look and probably much worse than that. However, after the remarkable events of Saturday, that's exactly what will be taking place this evening.
9.38pmAfter Nishikori beat Novak Djokovic and Cilic thrashed Roger Federer, the number 10 and 14 seeds respectively will go toe-to-toe in the first major final not to involve one of Saturday's semi-finalists and Rafael Nadal for the first time since 2005. Does that make tonight's match any less exciting? Of course not! These two men have wowed the crowds in New York throughout the second week and they fully deserve their place in the final at Flushing Meadows.
9.40pmWe still have 20 minutes before the two finalists make their way out onto the Arthur Ashe Stadium court, so that gives us plenty of time to take a look at each man's run through to the final.
9.44pmLet's start with Kei Nishikori. He was already a star in Japan before this tournament, but his achievements over the past two weeks have transformed him into a global superstar. He had it easy during the opening week of the tournament before he met Milos Raonic in the last 16. Nishikori looked to be heading out when he fell two sets to one behind, but he fought back to win the match in the equal-latest finish at Flushing Meadows. Another five-set epic followed with Stanislas Wawrinka before he stunned the world of tennis by ousting Djokovic in four sets.
9.50pmAs for Marin Cilic, he was given a routine passage through to the second round when Marcos Baghdatis retired injured before comfortably getting past Illya Marchenko. Things turned difficult from the last-32 onwards as he required four sets to get past Kevin Anderson before Gilles Simon took him the distance in the fourth round. Many would have expected one of Tomas Berdych or Roger Federer to be too strong for the big-serving Croatian in the latter stages but both were brushed aside with ease.
9.53pmLet's take a quick look at how the tournament statistics match up. The majority of them are in favour of Cilic - who has served faster and more aces than his opponent while also spending two hours less on court, but Nishikori has hit as many as 90 more winners from the baseline. That could be the area in which the match is won or lost by the Japanese player.
9.56pmThis time 12 months ago, both players were in no shape whatsoever to challenge at the final major of the year. Nishikori was easily beaten by British player Dan Evans, who recorded six breaks of serves during a straight-sets victory, but it was even worse for Cilic, who had to sit out the tournament due to a drugs ban after after testing positive for nikethamide. What a difference a year makes...
10.01pmIt's showtime! The two players are making their way onto a half-full Arthur Ashe. Let's hope it fills up a bit later in the next half hour. The wind has played its part throughout the tournament and judging by the speed in which the flags are blowing, it could play a part here.
10.04pmRemarkably, this is the third time that Nishikori and Cilic have faced each other at the US Open in five years. Nishikori prevailed in five sets in 2010 but Cilic came through in four in 2012. This could be some decider.
10.07pmThere are sure to be a few nerves flying about. They've played big matches before, but nothing compared to this. Their games have been based on ferocious ball-striking, but I wouldn't be surprised to see them play a little tentative in the opening few games.
10.08pmThat's the warm-ups done. Strap yourself in, the 2014 US Open final is about to get underway. It will be Cilic to serve first.
Nishikori *0-1 CilicAn ace helps Cilic move into a 30-0 advantage but a sharp return from Nishikori will help him settle into the match. Cilic looks a little shaky and two errors gift the Japanese an early break point, but it's saved with a blistering cross-court forehand. It gives the Croatian the confidence that he needs to serve out the game.
Nishikori 1-1* CilicCilic is already looking to impose his size and power on Nishikori and it works as he advances to the net to put away a smash for 0-15. Nishikori throws up a couple of weak second serves to hand Cilic 15-30, but he finds his mark on the next delivery for 30-30. The Japanese seems to have the crowd on his side and he takes the next two points to level things up in these early stages.
Nishikori *1-2 CilicIt's an easy hold for Cilic, who takes four straight points during an error-strewn game for Nishikori.
Nishikori 2-2* CilicWe finally have a lengthy exchange from the baseline and it's Nishikori who comes through it with the point. Cilic gets back in the game at 30-15 but the wind forces the Croatian to miscue a return, and there's nothing that he can do when Nishikori unwinds on a forehand.
Nishikori *2-3 CilicAfter that near miss in the first game, Cilic isn't messing about on his serve. A 129mph and 134mph ace earn him 40-0 before Nishikori floats a return long to give the Croatian his second love-hold in a row.
Nishikori 2-4* CilicBREAK! Given their contrasting heights, you feel that Cilic could gain an advantage in certain parts of this match and he's all over Nishikori from the back of the court to earn three break points. The first two are saved with well-directed first serves but Cilic strikes on the third as Nishikori goes wide with a forehand. First strike to the Croatian.
Nishikori *2-5 CilicNishikori halts Cilic's run of 12 successive points on serve when the number 14 seed hooks wide, but Cilic crushes a forehand to establish a 30-15 advantage. He produces an even better forehand winner from corner to corner before sealing the game with a huge first serve down the middle. This is imposing stuff from Cilic.
Nishikori 3-5* CilicThe start of game eight is delayed by bizarre goings on with the balls. Nishikori believes that they are deflated but the umpire thinks otherwise. Nishikori doesn't let that distract him in moving to 30-15 but a well-struck backhand down the line takes Cilic two points from the set. The Japanese player holds on though, and he forces his opponent to serve for the first set.
Nishikori *3-6 CilicSET! This has been a superb first set from Cilic and he shows he is more than just about power as he glides into the net to execute a drop volley for 30-0. Nishikori then blazes long to give the Croatian three set points, with the first begin taken when Nishikori nets a backhand. First blood to Cilic, and he could be hard to stop.
Nishikori 3-6 1-0* CilicNishikori needs a quick start to this second set and he delivers with his best game of the match. A hold to 15 is sealed with an inside-out forehand down the line. The crowd's support of the Japanese star is growing.
Nishikori *3-6 1-1 CilicCilic records back-to-back aces for a 30-0 lead but he fires long of the baseline with a miscued backhand. It's a momentarily lapse from the Croatian though, who holds to 15 after a Nishikori error.
Nishikori 3-6 1-2* CilicBREAK! Trouble for Nishikori as he misfires off both wings to give another three break points to Cilic. Given the way Cilic is serving, it's potentially three set points. Nishikori saves the first two before a third is saved with a stunning drop shot from the back of the court. It's beautiful stuff. However, Cilic gets a fourth chance after smashing a forehand winner and the break is sealed when Nishikori sends a backhand into the net. It's going to be tough for Nishikori from here.
Nishikori *3-6 1-3 CilicNishikori has an opening at 15-30 when Cilic hooks a backhand wide, and two break points are brought up when Cilic dumps the same shot into the net. This is Nishikori's chance, but Cilic plays four nerveless points, smashing his forehand from side to side to draw the mistakes out of his opponent. That could be a pivotal moment in this match.
Nishikori 3-6 2-3* CilicDespite the disappointment of the last game, Nishikori comes out firing at the start of this one, blasting a forehand down the line to earn 30-0. A first serve then helps him to 40-0 but the 10th seed looks a little stiff walking to get his towel. He still holds to love though when Cilic goes long.
Nishikori *3-6 2-4 CilicNormal service is resumed as Cilic ruthlessly powers down a near-perfect game. Four first serves, three aces. Magnificent.
Nishikori 3-6 2-5* CilicBREAK! This has been a spectacular performance from Cilic and it's getting better and better. He brings up two break points after some huge shots inside the baseline and he's move a game away from a two-set lead when Nishikori nets.
Nishikori *3-6 3-5 CilicBREAK! It appeared to be plain sailing for Cilic but a couple of nervy backhands into the net give Nishikori a chance to get one of the breaks back. Like on the previous occasion though, the advantage quickly evaporates as Cilic winds up with his first serve and forehand, but Nishikori gets a third chance to break when Cilic incorrectly challenges a call and he strikes when Cilic blasts a forehand long.
Nishikori 3-6 3-6* CilicSET! A mixture of Nishikori finding some rhythm and Cilic losing his own is making the end of this set interesting, but after the Japanese gets to 30-15, Cilic fights back, and a netted smash gives the Croatian a set point. After a lengthy rally, Cilic takes his chance, middling a forehand that catches the baseline and he is one set away from his first major title.
Nishikori *3-6 3-6 0-1 CilicYou're a set away from winning the US Open. How do you open up your next service game? With three aces. Stunning stuff. However, the game isn't over and three mistakes from Cilic, including a double fault, allows Nishikori to get back to deuce. All of a sudden, the pressure is on, but Cilic catches the line several times during the longest rally of the match to earn advantage before he eventually comes through to edge ahead.
Nishikori 3-6 3-6 1-1* CilicNishikori must hold here or else Cilic could run away with the match. After the game gets to 30-30, Nishikori earns game point but he can't convert as he nets a backhand. However, he records his first ace of the match to bring up advantage before taking the game thanks to a Cilic mistake.
Nishikori *3-6 3-6 1-2 CilicCilic easily brings up 30-0 but the deficit is halved to the delight of the New York crowd as Nishikori forces Cilic to net. However, the 14th continues to show no mercy with his serving and forehand and he holds once more.
Nishikori 3-6 3-6 1-3* CilicBREAK! A well-aimed return gets Cilic off to a positive start but Nishikori is soon back on the offensive when he puts away a forehand. Cilic batters Nishikori into submission on the next rally for 15-30 and he has two break points when Nishikori nets. Is this the moment for Cilic? It could just well be. Nishikori saves the first chance but Cilic outlasts his opponent on the next and he is three service games away from a resounding victory.
Nishikori *3-6 3-6 1-4 CilicNishikori stops Cilic running away with the game with a fantastic forehand lob but the Croatian smashes his way into a 40-15 advantage. Some brilliant play from Nishikori keeps him in the game, and probably the match, but another smash from Cilic seals the a three-game advantage.
Nishikori 3-6 3-6 2-4* CilicThe crowd are still backing Nishikori - they want to get value for money - and it inspires their man to take charge of his service game with a forehand winner and heavy first serve. A love hold is confirmed when Nishikori powers another forehand down the line and there's definitely still life in the Japanese.
Nishikori *3-6 3-6 2-5 CilicWith the final line in sight, will Cilic start to get tight? Maybe. Two unforced errors in a row give Nishikori 15-30, and that quickly becomes two break points when the Croatian nets from the baseline. Cilic saves both, and he saves a third when Nishikori can't get a second serve over the net. The New York crowd are getting very rowdy towards Cilic - it's actually quite bad - but the Croatian lets out a huge roar after coming out on top in two rallies. The first saw a drop shot clip the net and beat Nishikori before the second ended with a crushing winner down the line. He's one game away.
Nishikori 3-6 3-6 3-5* CilicWith the crowd getting on his back, Cilic could do with winning this match here. After the first two points are shared, Nishikori finds the corner with a forehand winner but Cilic has 30-30 when the Japanese marginally misses the baseline with a backhand. Big moments here, but Nishikori serves out the game to put the pressure on Cilic.
Nishikori 3-6 3-6 3-6 CilicCHAMPIONSHIP! Pressure? What pressure? Cilic thunders down two massive serves for a 30-0 advantage. He's two points away. Nishikori then hooks a backhand wide and it's three championship points for Marin Cilic. This is surely the moment? Not straight away - he concedes a double fault! How's his nerves holding up now. Just fine! Cilic wins the US Open with a cross-court backhand. It's a stunning performance.
12.04amMARIN CILIC WINS THE 2014 US OPEN WITH A 6-3 6-3 6-3 WIN OVER KEI NISHIKORI!
12.07amWell it wasn't a great final, but Marin Cilic won't care. The Croatian has produced a scintillating performance to completely overwhelm a lacklustre Kei Nishikori, who seemed to be feeling the effects of a tiring run to the final. Congratulations to the number 14 seed and his team, who are led by Goran Ivanisevic.
12.09amCilic has won his last three matches - against Tomas Berdych, Roger Federer, and Nishikori - in straight sets. That's some achievement. It has been Cilic's night but credit should also go Nishikori - he has enjoyed a special two weeks and tennis in Japan will only go from strength to strength.
12.12amThat will be all from Sports Mole's coverage of this match and the 2014 US Open. We hope you enjoyed the tournament as much as we did, and we hope to see you again throughout the final couple of months of the season. There's still some big events right around the corner! Goodbye for now.