US Open champion Angelique Kerber officially became the oldest woman to debut at No. 1 in the WTA rankings, ending Serena Williams' record-tying run of 186 consecutive weeks in the top spot.
Monday's rankings are the first since February 2013 without Williams at No. 1.
The 28-year-old Kerber's rise from No. 2 was assured when Williams lost in the semifinals at Flushing Meadows.
Kerber went on to beat Karolina Pliskova in Saturday's final for her second Grand Slam title of the season. She defeated Williams at the Australian Open in January, then was the runner-up to the American at Wimbledon in July.
She is the first woman from Germany to be ranked No. 1 since Steffi Graf, who has been a mentor for Kerber. Graf and Williams share the mark for most weeks in a row atop the WTA.
Williams is now No 2, followed by French Open champion Garbine Muguruza at No 3, Agnieszka Radwanska at No 4, Simona Halep at No 5, and Pliskova at a career-best of No. 6. Pliskova was No 11 before making it past the third round of a major for the first time and becoming the fourth woman to eliminate both Williams sisters during a Grand Slam tournament.
Roberta Vinci, the U.S. Open runner-up in 2015, dropped from No 8 to No 15 on Monday after losing to Kerber in the quarterfinals last week. Victoria Azarenka went from No 7 to No 11; she skipped the US Open because she is pregnant.
Novak Djokovic remained at No 1 in the ATP rankings despite losing to No 3 Stan Wawrinka in the men's final at Flushing Meadows on Sunday night. Andy Murray stayed at No 2.
Rafael Nadal gained one spot to No 4, and Kei Nishikori moved up from No 6 to No. 5. Roger Federer slid from No 4 to No 7 as he sits out the rest of 2016 while rehabbing his surgically repaired left knee.
Gael Monfils, who lost to Djokovic in the semifinals in New York, jumped from No 12 to No 8.
Saketh jumps to 137
Following his maiden appearance at the US Open Saketh Myneni on Monday achieved a career-high rank of 137 in singles in the latest list, issued by the ATP.
The 28-year-old Myneni, who will lead India in the Davis Cup tie against Spain, entered the main draw of the US Open after winning three rounds in the Qualifying event and jumped six places to 137.
However, out of action Yuki Bhambri plummeted to 219 after a steep loss of 48 positions in the ranking ladder and is now the third highest-ranked Indian behind Ramkumar Ramanathan, who is now 203 (loss of one position). Young Sumit Nagal was the next best at 380.
In doubles, Rohan Bopanna, who has opted out of Davis Cup tie against Spain citing a knee injury, lost a place to be 18th and was followed by leander Paes (63) and Divij Sharan (64), who improved by five slots.
Purav Raja was static at 73.
In the WTA rankings, Sania Mirza (9730) continued to be world number in doubles but now only five points separate her from fellow number one Martina Hingis (9725).
In the singles, Ankita Raina was best ranked at number 292, a loss of three places. She was followed by Prerna Bhambri (408) and Snehadevi Reddy (489).