Chris Connor was born Mary Jean Loutsenhizer on November 8, 1927, in Kansas City, Missouri, the younger daughter of a Western Union telegraph operator who taught her Morse code. The family moved to Jefferson City, Missouri, when she was thirteen, and she played first clarinet in her high school band, training she later credited with teaching her to read music and control her breath. She sang at a junior college graduation in 1945 and took the gender-neutral stage name Chris Connor while still in her teens. After high school she sang with a University of Missouri big band whose book included Stan Kenton arrangements, and she worked night gigs with her friend Bob Brookmeyer while holding a secretary's job in Jefferson City. She moved to New York in 1949, learned that Claude Thornhill was auditioning girl singers, and joined his vocal group, the Snowflakes. The group cut only one session with her, "There's a Small Hotel" in 1949.

By spring 1952 she had joined clarinetist Jerry Wald's band and recorded four sides with it, including her first single, "You're the Cream in My Coffee." Later that year June Christy, then Kenton's vocalist, heard her on the radio and recommended her as her replacement. Connor recorded with the Stan Kenton orchestra in 1953, and her reading of "All About Ronnie" became the song most associated with her. She left the band that year, worn out by one-night stands that could be 300 miles apart, and took on the manager Monte Kay, who booked her as a solo act at Birdland. Gus Wildi, president of the young Bethlehem label, heard her there and signed her as its first full-time jazz artist.

Her first Bethlehem singles were novelties she disliked, but the label's producer Creed Taylor wanted a cool-jazz vocal album, and Chris Connor Sings Lullabys of Birdland (October 1954), recorded with the Ellis Larkins trio, established both the singer and the label. Chris Connor Sings Lullabys for Lovers followed in December 1954 with a small group, and This Is Chris (August 1955) added a larger cast that included pianist Ralph Sharon, trombonists J.J. Johnson and Kai Winding, and flutist Herbie Mann. Billboard's jazz chart for the week ending April 23, 1955, had the first two albums at numbers one and two.

In 1956 she moved to Atlantic, where Chris Connor (April 1956) was the label's first jazz vocal LP. Its three sessions paired her with a 19-piece orchestra conducted by Ralph Burns, a quartet led by pianist John Lewis with Oscar Pettiford on bass, and a band that included trumpeter Nick Travis and tenor saxophonist Zoot Sims. He Loves Me, He Loves Me Not (November 1956) set her against a Burns string orchestra and reached the top ten of Billboard's best-selling jazz albums that December. The single "I Miss You So" reached number 34 on the Hot 100 in 1956 and "Trust in Me" reached number 95 in 1957, her only two charted singles. She made about a dozen albums for Atlantic through 1962, among them Chris Connor Sings the George Gershwin Almanac of Song (1957), A Jazz Date with Chris Connor and Chris Craft (both 1958), Sings Ballads of the Sad Cafe and Witchcraft (1959), Chris in Person and A Portrait of Chris (1960), and, with Maynard Ferguson's orchestra, Double Exposure (recorded December 1960 to January 1961). A companion set from the same period, Two's Company, was issued on Roulette.

She did not stay with Atlantic and signed with Kay's new FM label, which issued two albums, the live At the Village Gate (1963) and A Weekend in Paris (1964), before it folded. ABC-Paramount released Sings the Gentle Bossa Nova (1965) and Now! (1966), and in January 1969 she recorded Softly and Swingin' in Tokyo with drummer George Otsuka's trio, one of several albums made for Japanese labels. She recorded only sporadically until the mid-1970s, then returned to regular work for Progressive (Sweet and Swinging, 1978), Stash (Love Being Here with You, 1984), Contemporary (Classic, 1987, and New Again, 1988) and Japan's Alfa label. In 1991 she recorded As Time Goes By for Enja with the Hank Jones trio. In 1984 she shared the Eastworld album Three Pearls with Ernestine Anderson and Carol Sloane. Her final albums, Haunted Heart (2001), I Walk with Music (2002) and Everything I Love (2003), were made for HighNote. Her last public show, in 2004, was at a New York club with Anita O'Day.

Connor lived in Toms River, New Jersey, and passed away there on August 29, 2009, at 81, of cancer. Her longtime partner and manager was Lori Muscarelle.

Connor was a cool-school singer, known for a husky, lush sound, very little vibrato except on special occasions, and inventive alterations of the rhythm of ballads. Her obituaries placed her with Anita O'Day, June Christy, Chet Baker and Julie London; the New York Times said she emulated O'Day and Christy, and O'Day's own profile counts Connor among the singers O'Day influenced. AllMusic's Alex Henderson singled out her versions of "Lush Life" and "Lullaby of Broadway." The critic Will Friedwald called her Bethlehem work superb, and she thought those albums succeeded because their sparse accompaniments, often a small group built around a piano, left her voice uncluttered. Her repertoire was the American songbook, ballads above all, and her 1956 album Chris Connor appears in the Penguin Guide to Jazz Core Collection. In Japan, the singer Kimiko Kasai has said that hearing Connor sing "All About Ronnie" on the radio as a teenager set her on the path to jazz.