The American skater won the free-skate program en route to becoming the first woman in 43 years to capture a fifth world title.
Russia's Elena Sokolova took home the silver medal, while Fumie Suguri of Japan won bronze.
Canadian champion Jennifer Robinson of Windsor, Ont., participating in what could be her final world championships, finished ninth overall. Joannie Rochette of Berthierville, Que., was 17th at her first-ever worlds.
Gold medallist Michelle Kwan waves to the crowd from the podium at the world figure skating championships in Washington, D.C., on Saturday. (CP/Paul Chiasson)
The 22-year-old Kwan was the class of the field Saturday. She thrilled the MCI Centre crowd with six triple jumps, although she didn't land any triple-triple combos. Even though it wasn't her most technical performance, Kwan received many 5.9s and two perfect marks of 6.0 for her artistic impression.
Eight of the nine random judges used for the official scoring selected Kwan first overall, while one chose Sokolova.
Kwan, who first captured a world title at the 1996 championships in Edmonton, has been on the world podium eight years in a row.
"I worked hard this season but I didn't put a lot of pressure on myself," said Kwan. "I still don't believe it. Wow. I have no words."
The California native is the first woman since American Carol Heiss to earn five world championship gold medals. Germany's Katarina Witt came close in the 1980s, winning four gold medals.
Kwan is still a long way from reaching the record of 10 held by Norway's Sonja Henie, the last in 1936.
For Robinson, a ninth-place showing capped a satisfying week.
"I was really happy with the performance but not thrilled with the triple-triple not being in," said the Canadian champion, who finished eighth one year ago.
"I was disappointed with that but happy with the entire week as a whole, keeping it together and feeling really confident and performing well."
Robinson didn't land a triple-triple combo on Saturday, something she'd done in the qualifying session. However, she landed six triple jumps in the free-skate.
Things weren't quite as smooth for the 17-year-old Rochette. She struggled through three falls Saturday and was happy to have her first world championships come to a close.
"It was very hard," said Rochette. "It was not what I planned to do.
"I was trying to do way better than that. I'm really mad now and I want to go back home and try harder to not have this happen again. I learned a lot of things skating with Michelle Kwan and all those other stars that really helped me. It will help my motivation when I get back home. I know what I need to work on and what I need to improve for next year."
Despite Robinson's top-10 result, this year's event extends Canada's gold-medal drought at the women's worlds to 30 years, when Karen Magnussen claimed the title in 1973.
Elizabeth Manley is the only other Canadian skater to step on the world championship podium since Magnussen's victory, when she captured a silver in 1988.
with files from Canadian Press
