RHODA” star Valerie Harper has been slapped with a $2 million lawsuit – for allegedly keeping her cancer diagnosis secret!

Broadway bigshot Matthew Lom­bardo claims in court papers that Harper, 74, didn’t tell him about her health woes when she signed to star in his play, “Looped.”

“Valerie is disgusted over this lawsuit,” revealed a source close to her. “As far as her cancer is concerned, she’s in better shape now than she was a year ago. But she’s not out of the woods yet.”

In his shockingly insensitive suit, Lombardo claims Harper and her husband, Tony Cacciotti, “were both aware” that she’d been diagnosed with lung cancer in 2009, but “knowingly withheld the truth” from him.

Despite the dire diagnosis, Harper played Hollywood legend Tallulah Bankhead in his play “Looped” and earned a 2010 Tony nomination for the role.

In January 2013, she was in rehearsals for a national tour of the play when she found out the cancer had spread to her brain – and was told she had just three months to live.

The Emmy-winning sitcom star dropped out of the production that month but filed a lawsuit demanding that she be paid because she was inca­pacitated for health reasons.

Lombardo filed a countersuit in Manhattan Federal Court in which he and the producers are seeking $500,000 to recover costs for replacing Harper (with Stefanie Powers) on short notice, plus another $1.5 million in damages.

Harper starred on “The Mary Tyler Moore Show” as Mary’s pal Rhoda Morgenstern from 1970 to 1977. She headlined her own spinoff, “Rhoda,” from 1974 to 1979, appeared on “Desperate Housewives” in 2011, and competed on “Dancing with the Stars” after her brain cancer diagnosis.

“Valerie doesn’t feel that she owed it to anyone to reveal her cancer,” said the source. “And she certainly doesn’t need this kind of stress.”