For the first time in WTA Tour history, the first 18 tournaments of the year yielded 18 different champions. No.2 Petra Kvitova snapped the unprecedented streak on Sunday when she won her first Porsche Tennis Grand Prix title and second title of the season.

In addition to leading the tour in titles, Kvitova is also the only woman to make more than two finals so far this season:

Players with Multiple Finals in 2019:

Kvitova: 4 (Sydney, Australian Open, Dubai, Stuttgart)
Pliskova: 2 (Brisbane, Miami)
Andreescu: 2 (Auckland, Indian Wells)
Barty: 2 (Sydney, Miami)
Kenin: 2 (Hobart, Acapulco)
Vondrousova: 2 (Budapest, Istanbul)

*Bold denotes title win

2019's 18-champion streak was like nothing the tour had ever seen. Since 1986 when the tour readjusted its schedule to begin in January, there have been only three instances of a streak of different champions extended past the first two months of the season. Kvitova did not pick up her second title of the year until April. 

First to Two Titles:

2019: Kvitova - Sydney, Stuttgart
2018: Kvitova - St. Petersburg, Doha
2017: Pliskova - Brisbane, Doha
2016: Stephens - Auckland, Acapulco*
2015: Halep - Shenzhen, Dubai
2014: Li - Shenzhen, Australian Open
2013: Radwanska - Auckland, Sydney
2012: Azarenka - Sydney, Australian Open
2011: Kvitova - Brisbane, Paris Indoors
2010: Dementieva - Sydney, Paris Indoors
2009: Dementieva - Auckland, Sydney
2008: Henin - Sydney, Antwerp
2007: Henin - Dubai, Doha
2006: Mauresmo - Australian Open, Paris Indoors
2005: Sharapova - Tokyo (February), Doha
2004: Henin - Sydney, Australian Open
2003: S. Williams - Australian Open, Paris Indoors
2002: Hingis - Sydney, Tokyo
2001: Henin - Gold Coast, Canberra
2000: Davenport - Australian Open, Indian Wells*
1999: Hingis - Australian Open, Tokyo
1998: Schnyder - Hobart, Hanover
1997: Hingis - Sydney, Australian Open
1996: Seles - Sydney, Australian Open
1995: Graf - Paris Indoors, Delray*
1994: Graf - Australian Open, Tokyo
1993: Seles - Australian Open, Chicago
1992: Sabatini - Sydney, Tokyo
1991: Novotna - Sydney, Oklahoma City
1990: Zvereva - Brisbane, Sydney
1989: Navratilova - Sydney, Tokyo
1988: Shriver - Brisbane, Sydney
1987: Mandilikova - Brisbane, Australian Open

*Title won in March

In addition to the unprecedented level of depth and parity, 2019 has seen a concerted youth movement develop. The tour has already crowned three teenage champions - Bianca Andreescu, Amanda Anisimova, and Dayana Yastremska - and the tour's four biggest titles of the hardcourt season were won by players aged 22-and-under. As a result, over the course of the 18-tournament streak, the average age of WTA champions was the lowest it's been since 2006.

Here's a look back at the 18 champions who spread the wealth over the first 18 tournaments of the year:

Week 1

Karolina Pliskova: Brisbane International (d. Lesia Tsurenko, 4-6, 7-5, 6-2).

The Czech has enjoyed a fantastic start to the season, and it was all forshadowed in her strong run to the title at the season's first Premier tournament. The Czech would go on to make the Australian Open semifinals and cap off her spring hardcourt season by making her first Premier Mandatory final at the Miami Open.

Aryna Sabalenka: Shenzhen Open (d. Alison Riske, 4-6, 7-6, 6-3)

Sabalenka picked up right where she left off in 2018, kicking off her year with her third career title in Shenzhen. Though she has made just one quarterfinal or better since (St. Petersburg SF), the Belarusian made her Top 10 debut after the Australian Open and has remained a big threat in every draw. 

Julia Goerges: ASB Classic (d. Bianca Andreescu, 2-6, 7-5, 6-1)

Julia Goerges took home the title in Auckland for the second consecutive season, but the tournament will be remembered as the week Canada's 18-year-old phenom Bianca Andreescu introduced herself to the WTA's elite. It was a remarkable run for Andreescu, who made her first WTA final as a qualifier, defeating Caroline Wozniacki, Venus Williams, and Hsieh Su-Wei en route. 

Week 2

Petra Kvitova: Sydney International (d. Ashleigh Barty, 1-6, 7-5, 7-6)

In a final that would also foreshadow big things for both women, Kvitova dug deep to edge Barty in a third-set tiebreak to take home her 6th title in 12 months, a tour-best. Barty would say later that the loss was the toughest moment of her career.

"That hurt, for sure," Barty said. "I mean, I think that's why I keep coming back. That's why I love the sport is that you have these amazing moments and you have these heartbreaking moments. But the journey in the middle is pretty bloody good."

Sofia Kenin: Hobart International (d. Anna Karolina Schmiedlova, 6-3, 6-0)

The youth movement in 2019 kicked off in earnest with 20-year-old Sofia Kenin's dominant march to her first WTA title in Hobart. The American lost just 33 games in 5 matches, the fewest games lost per match en route to a title this season. The result was no surprise to anyone who watched the youngster's two performances at the end of the season in the Fed Cup final, which saw her gamely battle and elevate her game in a great effort against the Czechs. 

Weeks 3 & 4

Naomi Osaka: Australian Open (d. Petra Kvitova, 7-6, 5-7, 6-4)

It took a gutsy effort from Osaka to snap Kvitova's 11-match win streak, a streak during which the Czech lost just one set. But in a match that would determine the No.1 ranking, Osaka found a way to put three squandered three match points in the second set behind her to edge Kvitova in the third to become the first woman to win her first and second Slam titles back-to-back since Jennifer Capriati in 2001 and the first to win back-to-back Slams since Serena Williams in 2015. 

READ: Osaka hits back at critics, preaches perspective after Stuttgart run

Week 5

Kiki Bertens: St. Petersburg Ladies Open (d. Donna Vekic, 7-6, 6-4)

2018 was the season of Bertens' transformation from a clay-court specialist to an all-court threat, bolstered by her stunning run to the biggest title of her career in Cincinnati last summer. After a disappointing January, Bertens rebounded by dropping just 32 games en route to her third hardcourt title in seven months. 

Vekic's week in St. Petersburg was also notable. Having started her season with a run to the Brisbane semifinals, the quickly-improving Croatian made her first Premier final and remained a threat on hardcourts, making yet another semifinal in Acapulco. 

Dayana Yastremska: Toyota Thailand Open (d. Ajla Tomljanovic, 6-2, 2-6, 7-6)

The talented 17-year-old Ukrainian won her first WTA title last fall in Hong Kong and she became the first active teenager to tally two titles after winning in HuaHin. 

Week 6 - Off (Fed Cup)

Week 7

Elise Mertens: Qatar Total Open (d. Simona Halep, 3-6. 6-4, 6-3)

The 23-year-old had a breakout season in 2018, making the Australian Open semifinals and winning three titles. The Belgian took one more step forward in Doha, defeating Kiki Bertens, Angelique Kerber, and Simona Halep in succession to take home her first Premier title. 

The week also signaled Simona Halep's rise in form and confidence. After injury and a coaching change complicated her pre-season, Halep finally made her first quarterfinal or better, and would go on to make the quarterfinals or better at two of her next three tournaments. That run would put Halep one match away from reclaiming the No.1 spot from Osaka, a quest ended by Pliskova in the Miami semifinals. 

Week 8

Belinda Bencic: Dubai Duty Free Tennis Championships (d. Petra Kvitova, 6-3, 1-6, 6-2)

Score another one for Generation Next over Generation Now. One week after Mertens bested Halep in Doha, Belinda Bencic, once the torch-bearer for the ever-talented Generation 1997, sealed her resurgence with a dramatic week in Dubai. The then 21-year-old won four consecutive three-set battles over four consecutive Top 10 players - Sabalenka, Halep, Svitolina, and Kvitova - to win her first Premier 5 title since winning Toronto in 2015.

In a prime example of the small margins that have dictated the season, Bencic saved six match points against Sabalenka, winning in a deciding tiebreak, and also edged Svitolina in a deciding tiebreak. Bencic would go on to build a 12-match win-streak, adding wins over No.1 Osaka and Pliskova in Indian Wells to make her first Premier Mandatory semifinal a few weeks later. 

Champions Corner: Bencic motivated by Osaka, Kvitova - 'We all inspire each other'

Alison Van Uytvanck: Budapest (d. Marketa Vondrousova, 1-6, 7-5, 6-2)

The Belgian successfully defended her title in Budapest, but the week served as a massive springboard for 19-year-old Vondrousova. The talented Czech leftie spent much of 2018 battling injury, but her run to the Budapest final was a big lift. She would go on to make back-to-back quarterfinals in Indian Wells and Miami and another final in Istanbul, posting a 20-4 record across all levels since the Australian Open. 

Week 9

Wang Yafan: Monterrey (d. Sofia Kenin, 2-6, 6-3, 7-5)

Between Osaka's rise to No.1, Hsieh Su-Wei's career season, Wang Qiang's continued growth as a big-tournament threat, and Wang Yafan's maiden title in Monterrey, it's been a strong 2019 for Asian tennis. Wang Yafan scored two big back-to-back wins over Vekic and Kenin to take the trophy, while Kenin added her name to the short list of just five women to make multiple finals this season.

Weeks 10 & 11

Bianca Andreescu: BNP Paribas Open (d. Angelique Kerber, 6-4, 3-6, 6-)

Andreescu made good on her earlier Auckland run, becoming the youngest woman to win a Premier Mandatory tournament. And she did it in style. Coming into the tournament ranked a career-high No.60 and having won 10 of her last 11 matches at all levels, Andreescu engineered a gritty giant-slaying run, defeating Garbiñe Muguruza, Elina Svitolina, and Angelique Kerber in succession to become the youngest woman to win Indian Wells since Serena Williams. 

Andreescu would continue her winning ways in Miami, extending her win-streak to 10 before injury forced her to retire in the Round of 16 to Anett Kontaveit. With a 20-4 tour-level record, only Kvitova, Pliskova, and Bencic have won more matches than the Canadian.

Champions Corner: Bianca Andreescu - 'I really think that anything is possible at any age'

Weeks 12 & 13

Ashleigh Barty: Miami Open (d. Karolina Pliskova, 7-6, 6-3)

No player has a better winning percentage through the first 18 events of the season than Barty. Her 18-3 record catapulted her into the Top 10 for the first time after scoring another big title for Generation Next in Miami. With Barty's Miami win, the four biggest tournaments of the first four months of the season will have been won by players aged 22-and-under:

Australian Open: Osaka (21)
Dubai: Bencic (21)
Indian Wells: Andreescu (18)
Miami: Barty (22)

Champions Corner: Ashleigh Barty - 'Looking back, I didn't have to prove anything'

Week 14

Madison Keys: Volvo Car Open (d. Caroline Wozniacki, 7-6, 6-3)

Keys came into Charleston, her least favored surface, having not beaten a Top 150 player since the Australian Open and riding a three-match losing streak. She walked away with her first title on clay, with impressive wins over Sloane Stephens and Wozniacki. 

Asked about the season's parity, Keys summed it up best: 

"Everyone is good. Everyone is playing well. Everyone is playing well at certain times of the year to win titles. Why not me? And I think it's the beauty of the WTA right now is that, yes there's been a bunch of different winners but not one has been like, 'Oh it's shocking'. Everyone's like, well yeah, she's really good, duh. Like how did you not think that was going to happen? 

"So the fact that there's been that many just shows how great women's tennis is right now. It is definitely a great moment to be able to try to put together some matches and get a win and know that even if you have a not great week or not great two weeks, you can still come back and if you find your game, you can be holding the Charleston trophy." 

Champions Corner: Madison Keys comes to terms on clay

Garbiñe Muguruza: Abierto GNP Seguros (d. Victoria Azarenka, 6-1, 3-1, ret.)

Having made two quarterfinals heading into her title defense in Monterrey, the former No.1 notched her first title of the year with a solid title run. Equally notable was Azarenka making her first final since her return from maternity, building on the form that saw her play one of the best straight-set matches in recent memory, a 7-5, 6-3 loss to Serena Williams in Indian Wells. 

Week 15

Amanda Anisimova: Claro Colsanitsas Open (d. Astra Sharma, 4-6, 6-4, 6-1)

Anisimova became the third teenage champion of the season in Bogota, winning her first WTA title with a strong comeback against rising Australian talent Astra Sharma in the final. The signs were there early in the season for Anisimova, when she knocked out Sabalenka in the third round of the Australian Open to make her first Round of 16 in just her third main draw at a major. 

Polona Hercog: Samsung Open (d. Iga Swiatek, 6-3, 3-6, 6-3)

The Slovenian came through to win her first title since 2012 and became the second-oldest champion of the 2019 season, holding off 17-year-old Polish phenom Iga Swiatek in the final. But by making her first WTA final, Swiatek, the reigning Wimbledon girls champion, became the highest-ranked player from Poland.