MEXICO CITY -- Poland's Iga Swiatek overwhelmed Jessica Pegula of the United States 6-1, 6-0 to claim the WTA Finals on Monday and regain her world No 1 ranking.

Second seed Swiatek broke Pegula five times and won the final 11 games in a 59-minute slaughter. The 22-year-old collected six out of her total 17 career titles this season and finishes as world No 1 for a second straight year.

"The team that's been with me the whole season, we had many ups and downs. This is for sure an up. We will for sure have many more if we keep working like that," Swiatek said after the game.

"She clearly really wanted that ranking. I mean, you could tell by the way she was competing here. ... She was, like today, crushing people," Pegula said.

Laura Siegemund of Germany and Vera Zvonareva of Russia won the doubles title by beating Nicole Melichar-Martinez of the US and Ellen Perez of Australia 6-4, 6-4.