The win marked the first women's Grand Slam doubles title for former French Open singles champion Ostapenko and Kichenok, who also reached the final together at this year's Australian Open.
We are a really great team and I think it was just an amazing two weeks," Ostapenko said during the on-court trophy presentation.
"We didn't expect anything, we were just playing better and better every match, we didn't lose one set, so it was a really good tournament."
Ostapenko and Kichenok broke in the second game for an early advantage and, after the Chinese-French pairing got the set back on serve, had a massive hold in an eight-deuce game during which they fought off five break points for a 5-4 lead.
From there, Zhang was unable to keep the stanza alive and ultimately gifted the frame to her seventh-seeded opponents with a double-fault on the second set point.
In the second set, Zhang and Mladenovic broke early for a 2-0 lead but Ostapenko and Kichenok broke the Chinese for a third time to reach 3-3 and broke the Frenchwoman at love to reach 5-3 before Ostapenko closed out the match on her serve.
"I still have goosebumps after match point. It feels amazing," said Kichenok, who now has two Grand Slam titles after winning her first at the Wimbledon mixed doubles event in 2023.
"I'm blessed to have such a partner by my side on the court. Thanks for carrying me these two weeks."