Halep beat Williams in Saturday's final with surprising ease, 6-2, 6-2.
Coco Gauff's magical run from a wild-card entry in qualifying all the way to the fourth round at the All England Club allowed her to move into the WTA's top 150 for the first time.
The 15-year-old American rose 172 places to No. 141 from No. 313 before the tournament. Gauff was the youngest player to ever qualify for the main draw at Wimbledon, then beat five-time champion Venus Williams on the way to reaching the fourth round. That is when Gauff lost to eventual champion Halep.
Two other big jumps came from Barbora Strycova of the Czech Republic and Lauren Davis of the U.S.
The 33-year-old Strycova became the oldest first-time Grand Slam semifinalist in the professional era before losing to Williams, allowing her to move up 22 places to No. 32. Strycova also took over at No. 1 in the doubles rankings on Monday by winning that title at Wimbledon.
After losing in qualifying, Davis made it into the main draw when someone else withdrew. She then eliminated Angelique Kerber in the second round to become the first "lucky loser" to beat a defending champion at a major in the professional era and went up 13 spots to 75th.
Kerber dropped from No. 5 to 13th.
French Open champion Ash Barty remains at No. 1 in singles, followed by two-time major champion Naomi Osaka and Karolina Pliskova.
Wimbledon men's champ Novak Djokovic stayed atop the ATP rankings after his 7-6 (5), 1-6, 7-6 (4), 4-6, 13-12 (3) victory over Roger Federer on Sunday in the longest final in tournament history. Rafael Nadal is No. 2 and Federer is No. 3.
Roberto Bautista Agut, who lost to Djokovic in the semifinals, went from No. 22 to No. 13, equaling his career high.
Daniil Medvedev's third-round showing let him crack the top 10 for the first time at No. 10; he was ranked 13th before Wimbledon. Sam Querrey, beaten by Nadal in the quarterfinals, lifted his ranking by 26 spots to No. 39.