Whitson's 665 days off the planet - 288 days on this mission alone - exceeds that of any other American and any other woman worldwide.
She checked out of the International Space Station just hours earlier, along with another American and a Russian. Their Soyuz capsule landed in Kazakhstan shortly after sunrise on Sunday.
Whitson was the last one carried from the Soyuz. She immediately received a pair of sunglasses to put on, as she rested in a chair on the barren, wind-swept Kazak steppes. Medical personnel took her pulse, standard practice. She then received a bouquet of flowers with the greeting, "Welcome back, Peggy."
Besides duration, Whitson set multiple other records while in orbit: world's oldest spacewoman, at age 57, and most experienced female spacewalker, with 10. She also became the first woman to command the space station twice following her launch last November.
Returning cosmonaut Fyodor Yurchikhin logged even more time in space: 673 days over five missions. NASA astronaut Jack Fischer returned after 136 days aloft. The men flew up in April.
All three briefly held hands for a photo op, before being carried one by one in their chairs to the medical tent.
It was an emotional farewell to the space station for Whitson, Yurchikhin and Fischer. Before retreating into their Soyuz, they embraced the three colleagues they were leaving behind. Yurchikhin patted the inside of the station before floating into his Soyuz for the final time.
The station's newest commander, Randy Bresnik, noted the outpost was losing 1,474 days of spaceflight experience with the departure of Whitson, Yurchikhin and Fischer. Four years and two weeks, he pointed out.
"We are in your debt for the supreme dedication that you guys have to the human mission of exploration," Bresnik told them on the eve of their departure. He offered up special praise for Whitson - "American space ninja" - and wished them all Godspeed.
Yurchikhin is now No.7 on the world's all-time endurance list, followed by Whitson at No.8. The top spot belongs to Russian Gennady Padalka, with 879 days in space over five flights.
