Stephen K. Davis was born April 14, 1967, in Worcester, Massachusetts, and grew up in Binghamton, New York, in a household where jazz was played constantly. His maternal grandmother was a self-taught stride pianist who worked local restaurants, and his father took him to concerts, including sets by Elvin Jones and Art Blakey that he later named as formative. He was picking out bass lines on the piano by six, then worked through trumpet, baritone saxophone, and tuba before settling on trombone in his high school concert band. Two things sharpened him quickly as a teenager: three years in the Binghamton Youth Symphony, and the summer jazz workshop at SUNY Binghamton, where Bob Brookmeyer and Joe Lovano taught. He then went to the Hartt School at the University of Hartford, where he studied with the alto saxophonist Jackie McLean, graduating from Hartt's Jackie McLean Institute of Jazz in 1989.

McLean recommended him to Art Blakey, and Davis joined the Jazz Messengers in New York in December 1989, at twenty-two, taking the chair Frank Lacy was leaving. The band he walked into held trumpeter Brian Lynch, tenor saxophonists Javon Jackson and Dale Barlow, pianist Geoff Keezer, and bassist Essiet Essiet. The handover is audible on record: Chippin' In, cut at Van Gelder Studio on February 1 and 2, 1990 for Timeless, has Davis on three of its ten tracks and Lacy on the rest. Two months later came One For All, recorded April 10 and 11, 1990 at BMG Studios in New York for A&M, and it turned out to be Blakey's final studio album. Davis wrote and arranged its title track, "One For All (And All For One)," which gave the record its name and, six years later, gave a name to the sextet he would spend the next three decades in. Blakey died that October.

Davis moved back to Hartford in 1992, joined McLean's sextet for the next five years, and began teaching alongside his mentor at both Hartt and the Artists Collective, the Hartford institution McLean founded with his wife Dollie. He has been on the Hartt faculty since 1991 and has lived in the Hartford area ever since, working out of it rather than out of New York. With McLean he recorded Rhythm of the Earth (Antilles/Birdology), cut at Van Gelder Studio on March 12 and 13, 1992, and Fire & Love (1997), issued in Japan on Somethin' Else and in the United States and Europe in a nine-track version credited to Jackie McLean & The MacBand.

His own leader catalog began with The Moon Knows, recorded direct to two-track digital on August 16 and 17, 1994 with a Hartford band billed as The Explorers, and issued on Brownstone. Then came the long Criss Cross run that made his reputation: The Jaunt (recorded June 20, 1995 at RPM Studio, with Eric Alexander, Bruce Barth, Ugonna Okegwo, and Eric McPherson), Dig Deep (December 18, 1996), Crossfire (December 9, 1997), Vibe Up! (December 19, 1998), Systems Blue (May 29, 2001), Meant to Be (December 10, 2003), and Update (December 1, 2005, with Roy Hargrove and Peter Bernstein). Most were built from a small pool of players he has kept returning to for thirty years: Eric Alexander, Jim Rotondi, David Hazeltine, Joe Farnsworth, Mike DiRubbo, Nat Reeves, Harold Mabern, Peter Washington, and Larry Willis.

Two things happened almost at once in the mid-1990s that widened his working life. The first was One For All, the cooperative sextet he founded with Alexander, Rotondi, Hazeltine, Washington (later John Webber), and Farnsworth out of a standing engagement at Smalls in Greenwich Village. Its first record, Too Soon to Tell, was made on February 25, 1997 for Sharp Nine, and the band has stayed together ever since, moving through Sharp Nine, Criss Cross, and Smoke Sessions and reaching Big George with George Coleman in 2024. The second was Chick Corea's Origin, the acoustic sextet Corea built in 1997 with Davis on trombone, Steve Wilson and Bob Sheppard on reeds, Avishai Cohen on bass, and Adam Cruz, then Jeff Ballard, on drums. Davis held that chair until 2001, across Live at the Blue Note and the six-disc A Week at the Blue Note (both from a December 1997 residency), Change (1999), the Sony Classical Corea.Concerto with the London Philharmonic (1999), and the compilation Originations (2000).

Origin's Stretch Records connection produced two other things. One was Davis's own Portrait in Sound, recorded live to two-track at Sear Sound on March 20 and 21, 2000 and at Systems Two on April 25, with Corea as executive producer, Steve Wilson co-producing, and two tracks turned over to a second rhythm section of Brad Mehldau, Avishai Cohen, and Jeff Ballard. The other was his run through Cohen's own leader trilogy for the label: Adama (1998), where he plays on ten of the twelve pieces; Devotion (1999), where he is a full member of a band that also carried Jimmy Greene, Amos Hoffman, and Jason Lindner; and Colors (2000), where he takes three tracks alongside Avi Lebovich's trombone. Corea called him back nearly twenty years later for the Spanish Heart Band, whose Antidote (2019) won the Grammy for Best Latin Jazz Album.

From the early 2000s Davis became one of the most heavily booked trombonists in American large-ensemble jazz. He joined Freddie Hubbard's New Jazz Composers Octet in 2001, the Dizzy Gillespie All-Star Big Band under Slide Hampton's direction in the same year, the Jimmy Heath Big Band in 2006, and the Christian McBride Big Band in 2009. Three McBride albums he plays on have won the Grammy for Best Large Jazz Ensemble Album: The Good Feeling (2011), Bringin' It (2017), whose closing track is Davis's own "Optimism," arranged by him, and For Jimmy, Wes and Oliver (2020). His leader dates moved to Posi-Tone for Outlook (2008), Images: The Hartford Suite (2010), Gettin' It Done (2012), and For Real (2014), and then to Smoke Sessions, where he has made Say When (2015), Think Ahead (2017), Correlations (2019), Bluesthetic (2022), the archival Steve Davis Meets Hank Jones, Vol. 1 (2023, from a 2008 session with Hank Jones), and We See, taped live at Smoke over four nights in October 2023 and released in 2024.

The teaching has run in parallel the whole way. Davis was honored for more than thirty years of service at Hartt's Jackie McLean Institute of Jazz, joined the San Francisco Conservatory of Music's Roots, Jazz, and American Music program in 2019, and became professor of trombone in Berklee College of Music's brass department in the fall of 2022. He has also taught at the New England Conservatory, the University of Massachusetts's Jazz in July, the Skidmore Summer Jazz Institute, Jamey Aebersold's Summer Jazz Workshop, and the Stanford Jazz Workshop. He won the DownBeat Critics Poll's Rising Star trombone category in 1998 and was nominated for the Jazz Journalists Association's Trombonist of the Year award four years running, from 2010 through 2013. He plays regularly with his son, the guitarist Tony Davis, and with the vocalist Abena Koomson-Davis; both husband and wife appear on Natalie Merchant's Keep Your Courage (Nonesuch, 2023).

Davis plays in the line that runs from J.J. Johnson through the hard bop trombone chairs, and he is one of the few players of his generation who got the education directly: he learned the Jazz Messengers book from Art Blakey at twenty-two, and he learned phrasing from Jackie McLean for the better part of a decade after that. What critics single out is a lyrical, hard-swinging attack, a warm middle register, and an unusual evenness at speed, all of it aimed at the tune rather than at the horn's difficulties. AllMusic's Matt Collar calls him "one of the leading jazz trombonists of his generation," and All About Jazz has described that lyrical, hard-swinging style as the thing that first got him noticed in the 1990s. Steve Turre put him in the four-trombone front line of One4J, an explicit homage to J.J. Johnson, and Slide Hampton has used him in the World of Trombones. He is also a working composer with a body of tunes that other leaders program: "One For All (And All For One)" titled Blakey's last album, and "Optimism" gave Christian McBride's big band the closing track of a Grammy-winning record two decades after Davis wrote it for his own sextet.