The Oscar winner has opened up about her scandalous love life and open 30-year marriage to businessman Steve Parker in new book I'm Over All That, and accepts her three men in one day tale may shock many fans.
She says, "I wasn't into 'sexcapades', although I tried it once; I had three people in one day. It was on a political campaign, where everybody was doing the same thing (and) I just didn't wanna be left out.
"It was not my style at all; I'm a serial monogamist."
But that isn't to say MacLaine is a faithful girlfriend - or wife.
Despite her 30-year marriage, the Oscar winner tells TV chat show host Oprah Winfrey she's not fond of the institution and enjoyed a very special agreement with Parker.
She explains, "I had affairs and so did he, but we were very good friends. I loved the freedom and so did he.
"I've had an awful lot of lovers... and a lot of awful lovers."
In her chat with Winfrey, which aired in America on Monday, MacLaine confessed to romances with Robert Mitchum and French movie great Yves Montand.
MacLaine and Parker divorced in 1982.