It was the Latvian's first title on clay since her 2017 French Open Grand Slam victory.
Three-times defending champion Iga Swiatek was bundled out of the Qatar Open by Latvian Jelena Ostapenko, who beat the Polish second seed 6-3, 6-1 in the semi-finals on Friday to set up a final showdown with American Amanda Anisimova.
Rafael Nadal reclaimed top spot in the men's ATP rankings on Monday
Latvian Jelena Ostapenko believes she is getting better with every round and hopes to showcase the best of her abilities against five-time champion Venus Williams in the Wimbledon quarter-finals later on Tuesday.
Former number one Martina Hingis is not impressed by the current crop of young players whose main focus is on hitting harder, rather than developing an all-round game, the Swiss veteran said.
The popular Romanian, who had lost three major finals before Saturday, showed signs of nerves at first but recovered to outclass her 10th-seeded opponent.
The exodus of seeded players has been so spectacular that only one of the top 10 remains -- number seven Karolina Pliskova.
World number two and top seed Caroline Wozniacki, runner-up at the south coast event last year, cruised into the semi-finals with a 6-4, 6-3 win over Australia's Ashleigh Barty.
'It's very emotional. I've been waiting for this moment since I was 14'
Factbox on Latvian Jelena Ostapenko, who beat Romania's Simona Halep 4-6 6-4 6-3 to win the French Open on Saturday and claim her first grand slam title:
Former Wimbledon runner-up Eugenie Bouchard successfully negotiated the qualifying draw on Thursday, beating Colombian Mariana Duque-Marino 6-3, 6-2 to secure a spot in next week's main draw.
Serena, a six-times champion in New York who is seeded 17th, will start her campaign against Polish world number 60 Magda Linette and could face Venus in the third round before a possible fourth-round showdown with Romanian top seed Halep.
Novak Djokovic extended his unbeaten start to the season to 15 matches as he swatted aside German veteran Philipp Kohlschreiber 6-3 6-1 with ease on Wednesday to reach the Dubai Tennis Championships quarter-finals.
'I will put everything I have Saturday on the court'
Former men's champion Mats Wilander believes third seed Muguruza now looks like the most likely champion, having not dropped a set and thrashing Maria Sharapova on Wednesday.
Romanian Simona Halep showed the full extent of her defensive skills to beat Karolina Pliskova 6-4, 3-6, 6-3 and reach her second French Open final in Paris.
Three women in the field have topped the world rankings this season, incumbent Simona Halep and her predecessors Garbine Muguruza and Karolina Pliskova, but none of them have been able to kick on and cement their place as the tour's dominant player.
Djokovic, the ninth seed, was originally scheduled to play Australian Open semi-finalist Chung Hyeon but the 22-year-old South Korean withdrew with a back injury about an hour before the match was due to start.
Fourth seed Angelique Kerber's bid for consecutive Grand Slam titles ended when 29th seed Dominika Cibulkova defeated the German 3-6, 6-3, 6-3 in the US Open third round on Saturday.
The 16-year-old backed his aggressive backhand throughout the contest and went on to win 17 of his 23 points at the net to seal victory in 61 minutes.
IMAGES from Day 5 of the Wimbledon Championships at All England Lawn Tennis and Croquet Club on Friday.
With five of the top 10 in the current rankings aged 28 or older, form suggests another pair of seasoned campaigners could contest the title match at the French Open, which starts in Paris on Sunday.
Nadal, playing his first match since losing to Roger Federer in the Wimbledon semi-finals, fell behind 5-2 in the tiebreak before roaring back to prevail in his first career meeting with world number 53 Evans.