Iconic actress DIAHANN CARROLL is suffering from dementia, The ENQUIRER has learned.

The 78-year-old TV trailblazer – in 1968 she became the first African-American woman to star in her own television series, “Julia” – is still in the early stages of the disease. But a source says her memory loss is increasing, and the still-beautiful actress is devastated because she knows she may never sing again.

“It is such a sad thing to watch,” a friend said. “Sometimes she gets confused because she can’t remember someone or where she is at the moment.

“It’s heartbreaking.”

Dementia is an irreversible deteriora­tion of intellectual faculties, which affects memory, attention, language and prob­lem solving.

Diahann’s last major movie was “Peeples,” a Tyler Perry project with “Scandal” star Kerry Washington. It was released earlier this year.

“It was difficult for her to get through it,” the friend continued.

“But back then she was not so far gone and worked hard to finish the project. Diahann knows that was the last time she could do a movie, but she still hopes to make cameo appearances. She knows anything more than a line or two could turn into a disaster.”

But the stricken star is said to be even more devastated by the realization that she’ll never sing again.

“Diahann can’t remember all the lyrics to songs anymore,” revealed the source. “She hums in her home, but that’s it.”

Raised in New York’s Harlem, Diahann – who was nominated for an Oscar for her performance in the 1974 film “Claudine” – began modeling at 15 and acting at 18. After a career spanning six decades, she was inducted into the Television Academy Hall of Fame in 2011.

The four-times-married actress – who also appeared on the prime-time soap “Dynasty” – is estranged from her only daughter, writer Suzanne Kay Bamford.

“Fortunately,” the source added, “Diahann is surrounded by very close, loving friends who will make sure she is taken care of properly and with dignity.”