The "Friends" star posted on Instagram Monday to commemorate the first anniversary of her costar's death ... sharing a number of sweet photos of them together from their time making the NBC sitcom.

Jennifer kept the caption short, but sweet ... selecting a dove emoji and a healing heart emoji next to a simple "1 year" message.

The actress also notably tagged the late actor's foundation, aptly titled the Matthew Perry Foundation, that was launched by his loved ones in the aftermath of his passing in 2023.

Per the foundation, the organization's goal is to continue "Matthew’s enduring commitment to helping others struggling with the disease of addiction."

Matthew was found unresponsive in his hot tub at his home in Los Angeles on Oct. 28, 2023 ... he was later pronounced dead at the age of 54. His death was first reported as an apparent drowning, but the Los Angeles County Medical Examiner's Office confirmed in December that Matthew died from the acute effects of ketamine.

MP had been using ketamine infusion therapy for his mental health struggles ... but his last treatment came a week and a half before his death, prompting an investigation into how the drug got into his system.

Back in August, 5 people -- including 2 doctors, an alleged drug dealer known as the "Ketamine Queen," and Matthew's personal assistant -- were arrested in connection with his death.