Lady Gaga is grieving the loss of her "real true friend."

On Monday, the superstar actress and singer posted a tribute to her friend and collaborator Tony Bennett, who recently died at the age of 96.

Gaga hailed the legendary crooner, writing, "I will miss my friend forever. I will miss singing with him, recording with him, talking with him, being on stage together."

"With Tony, I got to live my life in a time warp. Tony & I had this magical power," her caption continued. "We transported ourselves to another era, modernized the music together, & gave it all new life as a singing duo. But it wasn't an act. Our relationship was very real."

The pair's friendship spanned more than a decade. They recorded two albums together, 2014's "Cheek to Cheek" and 2021's "Love for Sale," both of which won Grammy awards.

They also performed in the 2021 special, "One Last Time: An Evening with Tony Bennett and Lady Gaga."

She wrote on Instagram that while Bennett taught her about music, "he also showed me how to keep my spirits high and my head screwed on straight."

"He was an optimist, he believed in quality work AND quality life," she wrote. "Plus, there was the gratitude...Tony was always grateful."

Bennett's family went public in 2021 with his Alzheimer's diagnosis and in her post Gaga wrote, "I've been grieving the loss of Tony for a long time. We had a very long and powerful goodbye."

"Losing Tony to Alzheimer's has been painful but it was also really beautiful. An era of memory loss is such a sacred time in a person's life," she wrote. "There's such a feeling of vulnerability and a desire to preserve dignity. All I wanted was for Tony to remember how much I loved him and how grateful I was to have him in my life."

She also shared a message for others.

"If I could say anything to the world about this I would say don't discount your elders, don't leave them behind when things change," she wrote. "Don't flinch when you feel sad, just keep going straight ahead, sadness is part of it. Take care of your elders and I promise you will learn something special."