You may not know Marni Nixon, but you’ve definitely heard her voice.

Nicknamed the “The Ghostess with the Mostest,” the late, California-born Nixon was the playback singer for great actresses in movie musicals.

Hers was the dubbed voice of Audrey Hepburn in “My Fair Lady,” of Natalie Wood in “West Side Story” and of Deborah Kerr in “The King and I.”

Now Nixon’s teaching studio and her home — separate two-bedroom, one-bathroom co-ops — will go on the market for $1.05 million and $1.1 million, respectively.

They’re located inside 315 West End Ave., an eight-story building at 75th Street that dates to 1950.

(The units can be purchased separately or together, but they can’t be combined.)

Nixon passed away last summer at age 86 from breast cancer.

At first, she seemed to enjoy being the voice behind the scenes — sworn to secrecy by contract — but she eventually became the worst-kept secret in Hollywood, according to her New York Times obit. “It’s fascinating, getting inside the actresses you’re singing for,” she told The New York Journal-American in 1964. “It’s like cutting off the top of their heads and seeing what’s underneath. You have to know how they feel, as well as how they talk, in order to sing as they would sing — if they could sing.”

But after a while, the secrecy was irksome. “The anonymity didn’t bother me until I sang Natalie Wood’s song in ‘West Side Story,’ ” Nixon told The Times in 1967. “Then I saw how important my singing was to the picture. I was giving my talent, and somebody else was taking the credit.”

Even before — and after — her Hollywood days, Nixon was known as an concert singer, having performed solo with the New York Philharmonic and as a recitalist at Carnegie Hall.

The listing brokers for her properties are Halstead’s Douglas Kampsen and Charles Homet.