"I love you guys. It's an amazing event and I love to be here," Jelena says in post-match interview. "I'm really happy, I have no words, it was just my dream," she says.
"I feel amazing and I love to play here," she repeats in answer to some more questioning.
"Thanks to all my team, especially my Mum, my coach, all those who helped me and my agent," she adds.
She adds some nice respectful remarks about her opponent. We should spare a thought for Halep - who speaks with great dignity and class and vows to try again.
First unseeded player to win since 1933. And the Latvian national anthem rings out, the flag flutters on the flag pole and Jelena lifts the trophy over her head. Incredible.
CONGRATULATIONS to JELENA OSTAPENKO. The first, but almost certainly not the last grand slam title of her career!
SET 3, GAME 9: Halep serves to stay in the match. Ostapenko grabs the initiative and hits a succession of brutal winners that give her opponent no chance. OSTAPENKO WINS 4-6, 6-4, 6-3!
SET 3, GAME 8: This is amazing. Ostapenko is bossing Halep all over the court, but credit to the Romanian she is incredibly quick on her feet. Stats show Ostapenko has hit 50 winners against Halep's 8 - that tells you how aggressive she is. Jelena puts in her best service game of the match. 5-3. SHE IS ONE GAME AWAY FROM THE FRENCH OPEN TITLE.
SET 3, GAME 7: Ostapenko is rampant right now. She's super aggressive on Halep's second serve and it works - break point. WOW! An amazing net call lobs up in the air like a perfect drop shot. Halep can do nothing but watch as it drops good! Maybe the gods are with Jelena after all? 4-3!
SET 3, GAME 6: Just a reminder that this 20 year old is playing her first ever grand slam final - and she's playing like she was born to it. She's maybe realised that not every shot needs to be a winner and it's meaning we get a few longer rallies. Another deuce game. She ACES! And one exchange later, the game is hers. The crowd is starting to get behind her too! 3-3.
SET 3, GAME 5: You get the feeling Jelena would be quite happy to let Halep serve all the time. 30-40 break point, then yet again she hits the net in her search for an immediate winner. The second break point is a different matter as she crunches a line drive out of Halep's despairing lunge. 2-3.
SET 3, GAME 4: Ostapenko serves again. Now the serves are going in but she is hitting the net in her search for a big winner a bit too often. Halep has three break points. She takes the second. But again it was really Jelena beating herself up. 1-3.
SET 3, GAME 3: Some classy touches from Halep now, but she is being made to work for every point. Jelena has a chance for a winner but can't decide whether to smash or let the ball bounce and is caught doing neither. Halep takes the game. 1-2.
SET 3, GAME 2: Stats show Jelena has 59% first serves in, Halep 68%. That has kept Halep in this match. Now the Romanian tries to be more aggressive, but at times it still seems like Jelena versus Jelena, always going for the big shots. It pays off and Ostapenko holds her serve. 1-1.
SET 3, GAME 1: Here we go. Jelena has the momentum and remains aggressive, but will she run out of steam? Halep has definitely been playing within herself at times. Jelena has two break points of Halep's serve but can't put them away and Halep survives. 0-1.
SET 2, GAME 10: The crowd does a Mexican wave for some reason. Sit down and shut up you twits. Back with the match, Jelena seems to have eliminated her erratic serves and has three set points. She grabs the second one and the game, and the set! We will have a decider. SET TO OSTAPENKO 6-4!
SET 2, GAME 9: Jelena pounces on the first three serves and has three break points. She only needs one. Third break in a row and she leads 5-4 in second set. She'll be serving to take this to a decider! What a fighter!
SET 2, GAME 8: Time for Jelena's serve to come under more largely self-inflicted pressure and Halep breaks straight back. 4-4.
SET 2, GAME 7: Ostapenko is back on the attack! Three shots in a row that would have defeated any opponent and suddenly she has two break points against Halep's serve! It's back to deuce... she has ADV with a shot that defies physics and one incredible rally later featuring her trademark backhand smash she breaks Halep! She was 0-3 down and now it's 4-3 with her to serve!
SET 2, GAME 6: We're being treated to some super rallies now. Jelena had a super opportunity for a cross court winner but it got too big. Her serve is under pressure again 15-40... and she battles back to deuce! A gamble on a big second serve pays off to take ADV and she seald the deal. Brilliant! 3-3. Game on!
SET 2, GAME 5: Our girl is turning up the heat again, maybe sensing it's now or never. She has two break points against Halep's serve and needs to convert one of them - which she does! Break! "Malacis!" as they say round these parts. 2-3.
SET 2, GAME 4: Right, it's probably now or never as far as Jelena's serve is concerned. She needs a convincing game. A fourth double fault. For the first time Halep loses her cool after putting a shot wide. It's deuce yet again... Jelena saves a break point against her (that would surely have sealed the match) and a second! This girl has guts, that's for sure. A third break point is saved. She moves to ADV! The crowd senses this is a key moment... and she wins a scintillating rally. 1-3.
SET 2, GAME 3: Ostapenko still looks much happier attacking Halep's serve than serving herself. Meanwhile her opponent is staying ice cool, perhaps suspecting Jelena is just trying too hard to force winners. But Jelena is tenacious, fighting back to deuce. Halep deliver s a couple of quality, controlled forehands to seal the game. 0-3.
SET 2, GAME 2: A couple more mistakes from Jelena early on as she tries to force the pace again. This is a bit like a boxing match between a puncher and a counter-puncher. Sweet return from Halep gives her a break point, but Jelena digs deep to reach deuce. She spurns an ADV and is starting to look a bit frustrated again but won't give up. A series of ADV and DEUCE exchanges later Halep takes the break. 0-2.
SET 2, GAME 1: Jelena has shown she is in no way outclassed and much of the time actually looks the better player - btu she's also taking more risks than Halep who looks like she is happy to play a defensive game. But Jelena comes out swinging and takes a 40-0 lead against Halep's serve... which turns into deuce thanks to the quality of Halep's second serves. She finishes it off with an ace. Missed opportunity for Jelena. 0-1.
SET 1, GAME 10: Now would be an ideal time for Jelena's usual serve to kick in... Both these players are excellent returners, a nd it's noticeable that very few points are won by someone hitting the net. Halep piles on the pressure - it is her turn to raise her game.. 30-30... now Jelena does hit the net and it's set point to Halep.. which she takes. 4-6.
SET 1, GAME 9: Halep is really living on Jelena's unforced errors. But Jelena is starting to roll and her opponent looks a bit lethargic compared to the Latvian's power hitting and aggression. Stats show Jelena has made 10 unforced backhand errors as against zero for Halep. But Jelena is much the more aggressive. Deuce... and another super rally sees Halep seal the game. 4-5.
SET 1, GAME 8: I heard someone shout "Sarauj Latvija!" (Come on Latvia!) in the crowd as they came out. It seemed to work as her serve starts off much more solid... but then yet another double fault! From 40-15 Halep is back to deuce and Jelena's serve is under more pressure... but Jelena takes the game with the best rally of the match! 4-4.
SET 1, GAME 7: Halep starts strongly, with Jelena perhaps trying to force winners a bit too early in the rallies. But Jelena fights back deuce... outhinks her opponent to gain ADV... but just puts her winner too wide. Back to deuce. Halep takes the game and Jelena is a bit frutrated, doing a bit of gardenign with her racquet. She did have half a chance of another break there. But the questino now is can she get her serve firing? 3-4.
SET 1, GAME 6: Jelena's serve is still not fully functional and her toss is still troubling her. A second double fault gives away a 0-40 lead to Halep... and the game is hers. 3-3.
SET 1, GAME 5: Ostapenko is in full flight! She breaks Halep, taking the game 40-15 with more powerful precision. 3-2.
SET 1, GAME 4: Jelena starts with the first double fault of the match. But now the radar is starting to function - first with a beautiful controlled rally then a couple of frankly brutal winners! Final serve is vicious too and Jelena takes the game. This is promising, she really turned up the power in that game. 2-2.
SET 1, GAME 3: We get the first substantial rally, which Halep wins. And she takes the game to love after Jelena puts a couple of returns well past the baseline. She hasn't quite got her radar working yet. 1-2
SET 1, GAME 2: Jelena's serve isn't quite functioning properly. She had a couple of problems with her toss and a couple of way out first serves, but fights back from 0-40 to 30-40... then puts it wide. 1-1.
SET 1, GAME 1: Halep to serve. Ostapenko wins the first point of the game. And the second with a powerful return. And the third, controlling rally brilliantly. This is promising! And yes, she breaks Halep to love! 1-0 Jelena!
CONDITIONS appear to be pretty much perfect: bright and sunny with a slight breeze as they conclude the warm-up. 22C. These two have never played each other before.
And here they come onto court to a great ovation and somewhat bombastic music. Interestingly Jelena is slightly taller as they stand at the net for a photo.
"I'm going to just enjoy the match and do my best," says a smiling and remarkably relaxed-looking Jelena on her way to the court. She has an earphone in one ear - wonder what she's listening to!
OPPONENT: Romania's Simona Halep is the world number 4 and the definite favorite to win today, being the number 3 seed for the tournament. Here is her WTA info page. She's made the final twice before but lost both times, so certainly will not lack motivation.
MUM SPEAKS: In the coverage at the moment Jelena's coach and mother Jelena Jakovleva says her daughter is definitely ready for the task ahead and that conditions in Paris will suit her style of play.
LIVE COVERAGE: LTV7 is broadcasting the match on terrestrial TV in Latvia and you can also see it on the main LSM Latvian language page, though be aware that geo-blocking will likely apply to viewers outside Latvia - but wherever you are it's pretty certain someone will be broadcasting the French Open Final.