Ray Gelato was born Ray Keith Irwin in London on October 25, 1961, the son of an American serviceman stationed in Britain, and grew up on a council estate off Latimer Road in West London. His father's record collection supplied his first listening: swing bands of the 1940s alongside 1950s rock and roll and R&B. Two entertainers stood out, Louis Prima and Louis Jordan, and it was the tenor saxophone playing of Prima's sideman Sam Butera that made him want to learn the instrument. By the early 1980s he was working professionally.

In 1982 he teamed up with the French guitarist Patrice Serapiglia, who performed as Maurice Chevalier, and the pair became the Chevalier Brothers, a jump-and-jive act that began as a busking trio and grew into a five-piece club band with bassist Clark Kent, drummer John Piper and vibraphonist Roger Beaujolais. They won a talent contest at London's Camden Palace, played the Montreux and North Sea jazz festivals and toured Japan. It was Serapiglia who pushed Irwin to take the stage name Gelato and to sing regularly. The group issued a run of records in the mid-1980s, among them Live and Jumping (1985) and Buona Sera (1987), and folded in 1988.

Gelato's own band, the Giants of Jive, followed the same year. Kent and Piper came with him, and the debut album Giants of Jive (Blue Horizon, 1989) paired that rhythm section with piano, trumpet, trombone and a second reed player. He sang and played in the British film Scandal in 1989. The band became a large draw in Italy: a 1992 engagement at Carnegie Hall was filmed for Italian television, and Gelato Espresso (Durium, 1993) was issued there. The Giants of Jive broke up in 1994.

He started over immediately with the Ray Gelato Giants, a group that kept the stage energy but moved toward the standards and crooner repertoire of Nat King Cole, Duke Ellington, Dean Martin and Frank Sinatra. The Full Flavour (Linn, 1995) was recorded at Metropolis Studios in London on January 13 and 14, 1995, with the singer Claire Martin guesting on two tracks. In 1996 he sang on the soundtrack of the BBC One drama No Bananas with the John Altman Big Band. In Italy he recorded two albums with a local band, the Good Fellas: Gelato All'italiana (taped live in Bologna in May 1996) and Gangsters of Swing (1997), both for Durium. In 1998 the Giants began releasing records on Double Scoop Records, starting with The Men From Uncle, and the label has carried most of his output since.

The Giants became a fixture of the festival and private-party circuit. They played Umbria Jazz, the Montreal Jazz Festival, Molde, Marciac and San Sebastian, toured Italy and the United States, and in 2001 opened for Robbie Williams's Swing When You're Winning concert at the Royal Albert Hall. In 2002 the band played at Paul McCartney's wedding, and Gelato has said he performed twice for Queen Elizabeth II in a small room at the Ritz Hotel in London. The albums of those years leaned on Italian-American favorites and his own comic songs: Smokin' (2002), Ray Gelato (T2, 2004), Hey There (2006), Ray Gelato Salutes the Great Entertainers (2008), Hey Boy! Hey Girl! with the singer Kai Hoffman (March 14, 2011), Wonderful: The Lost Italian Songbook (2012) and Original Flavours (2015), a collection of songs he wrote himself, among them "A Pizza You," "Bar Italia," "My Last Meatball" and "Mambo Gelato." The band took over the Christmas season at Ronnie Scott's Jazz Club in London in 2015, following George Melly's long-running residency there, and the December engagement has become a fixture.

The more straight-ahead side of his work has grown in the last decade. We've Got a World That Swings (Linn, 2016), with the singer Claire Martin, was recorded in London on November 2 to 4, 2015 with pianist David Newton, bassist Dave Whitford and drummer Sebastiaan de Krom. With the Spanish tenor saxophonist Enric Peidro he co-leads a quintet that pays tribute to swing-era tenor players, and its album With All Due Respect is an instrumental record; Gelato has called it his first pure jazz album, with no vocals. The pair presented a second album, Exactly Like Us, in Barcelona on May 22, 2026. Between those projects came The Big Sound: Live in London (2019), Locked Down But Not Out (Double Scoop, released October 22, 2021) and Live at Ronnie Scott's (CD 2024, LP 2025).

In August 2026 Gelato appeared in the blind auditions of the fourteenth series of ITV's The Voice UK, singing his own song "A Pizza You" in the episode broadcast on August 22. Kelly Rowland and the duo Tom Fletcher and Danny Jones turned their chairs; he joined Rowland's team and was eliminated in the Battles that autumn. As of November 8, 2026, his own listings show Giants dates in Monfalcone, Italy on November 13, a Florida date on November 20, Southend on November 29, a Christmas show in Ware, Hertfordshire on December 5, and a run at Ronnie Scott's from December 19 to 23.

Gelato is best described as an entertainer working in the jump blues and swing revival tradition rather than as a straight-ahead jazz improviser, and his catalogue says so openly: a large share of it is Italian-American novelty songs, crooner standards and original comic numbers about everyday irritations, pitched at dancers and dinner audiences. He calls himself one of the last jazz entertainers, in the line of Cab Calloway, Louis Prima and Louis Jordan, and argues that critics have wrongly looked down on entertaining musicians. AllMusic hears his singing as loyal to Prima and his tenor playing as loyal to Sam Butera, and the same account notes that his repertoire moved toward the middle of the road when the Ray Gelato Giants replaced the Giants of Jive. Through those entertainers he came to Louis Armstrong, Count Basie, Ellington, Lester Young, Charlie Parker and Ben Webster. He has said that merely recreating the past is a waste of time, which is why original songs are now among the most requested numbers in his sets. AllMusic credits his success to hard work, good musicianship and a flair for showmanship, and Jools Holland is quoted as saying "He plays what he means, and means what he plays." The Daily Telegraph has called him the Godfather of Swing.