Kim Richards is opening up about the death of her ex-husband, Monty Brinson.

The Real Housewives of Beverly Hills star shared an emotional tribute to Brinson on Monday, posting a picture of herself and her ex, along with a touching memorial on Instagram.

"Yesterday I said goodbye to best the friend I've ever had in my life," Richards wrote in the heartfelt caption. "Monty was an amazing person with an amazing soul ... We shared over 30 years of Love & Happiness and brought a beautiful daughter into world. I am so grateful for all that we shared."

WATCH: Kim Richards' Ex-Husband Monty Brinson Dies At 58 After Long Battle With Cancer

"I love you Monty, my angel in heaven," the 51-year-old reality star concluded. "I know that we be together again one day. I will carry you in my heart always my love ... until then, may you rest in peace."

Brinson died Sunday at 58 after a long battle with lung cancer. A source close to Brinson confirmed to ET that he passed away in a medical facility surrounded by his family.

Richards and Brinson tied the knot in 1985 and remained together for three years until divorcing in 1988. The couple welcomed their daughter, Brooke, in 1986.

RELATED: Kim Richards and Monty Brinson's Daughter Shares Touching Photo of Father-Daughter Dance

After their divorce, the former couple remained close friends. Richards reportedly spent a lot of time by Brinson's side in recent weeks as his health declined, showing her support for her ailing ex.

For more on Brinson's life and his friendship with Richards, watch the video below.