Vittorio Giorgio Andre Spinetti was born on 2 September 1929 in Cwm, of Welsh and Italian descent from a grandfather who was said to have 'walked' from Italy to Wales to work as a coal miner, just to earn enough money to buy a plough. His parents, Giuseppe and Lily (née Watson), owned the chip shop in Cwm, over which premises the family lived and where Spinetti was born. Spinetti was the eldest of six, and his younger brother, Henry (born 1951), is a session Drummer. Spinetti was educated at Monmouth School and the Royal Welsh College of Music and Drama in Cardiff, of which he later became a Fellow. Early on, he worked as a waiter and factory worker. It was at the college that Spinetti met actor Graham Curnow, who became his partner.

Spinetti's last on-screen appearance was in the DVD release of the independent film Beatles Stories by US musician Seth Swirsky, issued to celebrate the 50th anniversary of the Beatles' first recording sessions at Abbey Road.

Spinetti's work in Joan Littlewood's Theatre Workshop produced many memorable performances including Fings Ain't Wot They Used T'Be (1959, by Frank Norman, with music by Lionel Bart), and Oh! What a Lovely War (1963), which transferred to New York City and for which he won a Tony Award for his main role as an obnoxious Drill Sergeant. He appeared in the West End in The Odd Couple (as Felix); in Chitty Chitty Bang Bang in the West End; and as Albert Einstein in a critically lauded performance in 2005 in a new play, Albert's Boy at the Finborough Theatre. He launched his own one-man show of witty reminiscences, A Very Private Diary, at the Edinburgh Festival Fringe.

Spinetti sprang to international prominence in three Beatles films in the 1960s: A Hard Day's Night, Help!, and Magical Mystery Tour. He also appeared on one of the Beatles' Christmas recordings. The best explanation for this long-running collaboration and friendship might have been provided by George Harrison, who said, "You've got to be in all our films ... if you're not in them me Mum won't come and see them – because she fancies you." But Harrison would also say, "You've got a lovely karma, Vic." Paul McCartney described Spinetti as "the man who makes clouds disappear". Spinetti would later make a small appearance in the promotional video for McCartney's song "London Town" from the 1978 album of the same name. His July 2010 performance of the song "Ob-La-Di, Ob-La-Da", at The Festival Theatre, Malvern, would later be made available on "The Beatles Complete on Ukulele" podcast.

Spinetti appeared in more than 31 films, including The Gentle Terror (1961), Sparrows Can't Sing (1963), The Wild Affair (1964), Becket (1964), Zeffirelli's The Taming of the Shrew (1967), The Biggest Bundle of Them All (1968), Can Heironymus Merkin Ever Forget Mercy Humppe and Find True Happiness? (1969), This, That and the Other (1969), Start the Revolution Without Me (1970), Under Milk Wood (1972), Digby, the Biggest Dog in the World (1973), The Great McGonagall (1974), The Little Prince (1974), The Return of the Pink Panther (1975), Voyage of the Damned (1976), Emily (1976), Hardcore (1977), Casanova & Co. (1977), Under the Cherry Moon (1986) and The Krays (1990).

Born in Cwm, Spinetti was educated at Monmouth School and the Royal Welsh College of Music and Drama in Cardiff, of which he became a Fellow. After various menial jobs, Spinetti pursued a stage career and was closely associated with Joan Littlewood's Theatre Workshop. Among the productions were Fings Ain't Wot They Used T'Be and Oh! What a Lovely War (1963), which transferred to New York City and for which he won a Tony Award. Spinetti's film career developed simultaneously; his dozens of film appearances would include Zeffirelli's The Taming of the Shrew, Under Milk Wood, The Return of the Pink Panther and Under the Cherry Moon.

From 1968 to 1969 Spinetti was a cast member of the Marty Feldman Sketch show "It's Marty," which was written by Barry Took, with contributions by John Cleese, Michael Palin and Graham Chapman, pre Monty Python,≈ as well as John Junkin, who appeared with Spinetti in Help!.§ Between 1969 and 1970 Spinetti appeared on Thames Television, alongside Sid James, as one half of Two in Clover over two series. A sitcom about two office workers who jack it all in to become farmers, he starred in all but one of the 13 episodes. His absence in episode No. 3 of the second series was covered by fellow Welsh actor Richard Davies, playing Spinetti's character's brother.

One of Spinetti's most challenging theatre roles was as the principal male character in Jane Arden's radical feminist play Vagina Rex and the Gas Oven, which played to packed houses for six weeks at the Arts Lab on Drury Lane in 1969. In 1980 he directed The Biograph Girl, a musical about the silent film era, at the Phoenix Theatre. In 1986 he appeared as Fagin in the musical Oliver!, which was the last professional production to use Sean Kenny's original stage design. He appeared on Broadway in The Hostage and The Philanthropist, and also acted in 1995 with the Royal Shakespeare Company, in such roles as Lord Foppington in The Relapse and the Archbishop in Richard III, at Stratford-upon-Avon, although this was not a happy experience for him.

In the 1970s Spinetti appeared in a series of television advertisements for McVities' (now United Biscuits) Jaffa Cakes, as "The Mad Jaffa Cake Eater", a turbaned, Middle-Eastern style character who rode a bicycle and surreptitiously stole and ate other people's Jaffa Cakes, prompting the catchphrase "There's Orangey!" He hosted Victor's Party for Granada. In 1979 he voiced Mr. Tumnus in the USA dubbed version of the 1979 animated adaptation of The Lion, the Witch and the Wardrobe as well as voice directing for the film. Later he voiced arch villain Texas Pete in the popular S4C animated TV series SuperTed (1982–84) and narrated several Fireman Sam audiobooks. In 1992, he voiced the King of the Rats in the British children's animated programme Tales of the Tooth Fairies (in the episode The Stolen Present) on BBC, produced by Welsh animation company Calon (formerly Siriol Productions). In 1995 he appeared in an episode of Bottom with Rik Mayall and Adrian Edmondson as Audrey the Maitre d'. Spinetti also starred in Boobs in the Wood with Jim Davidson, filmed for DVD in 1999.

During his later career, Spinetti acted with the Royal Shakespeare Company, in such roles as Lord Foppington in The Relapse and the Archbishop in Richard III, at Stratford-upon-Avon; and, in 1990, he appeared in The Krays. In 2008 he appeared in a one-man show, A Very Private Diary, which toured the UK as A Very Private Diary ... Revisited!, recounting his life story. Spinetti was diagnosed with prostate cancer in 2011 and died of the disease in June 2012.

Spinetti was gay; his partner of 44 years, Graham Curnow, died in 1997. The two shared a house and were openly non-monogamous. Curnow appeared in the 1959 British horror film Horrors of the Black Museum.

From 1999 to 2002 Victor played Max, the 'man of a thousand faces', in the popular Children's TV programme Harry and the Wrinklies, which also starred Nick Robinson (Goodnight Mister Tom) in the title role.

Spinetti's poetry, notably Watchers Along the Mall (1963), and prose appeared in various publications. His memoir, Victor Spinetti Up Front...: His Strictly Confidential Autobiography, published in September 2006, is filled with anecdotes. In conversation with BBC Radio 2's Michael Ball, on his show broadcast on 7 September 2008, Spinetti revealed that Princess Margaret had been instrumental in securing the necessary censor permission for the first run of Oh! What A Lovely War.

Paul McCartney paid tribute to Spinetti on his website: "Victor was a fine man, a great pal and a fantastic actor and someone I am proud to have known for many years. His irreverent wit and exuberant personality will remain in my memory forever. I will miss his loyal friendship as will all the others who were lucky enough to know and love the wonderful Mr Spinetti." At a memorial Service for Spinetti, attended by McCartney, the Beatles song "In My Life" was sung by Michael Ball. Preston FM scheduled a tribute broadcast, for 22 June, of a previously unaired in-depth interview with Spinetti, recorded when he visited Blackpool in July 2010, in Paul and Lucy Breeze's Best Kept Secrets in Conversation.

Spinetti had been diagnosed with prostate cancer in February 2011, after he collapsed onstage on Valentine's Day. He suffered a spinal fracture and discovered only by chance that he had a tumour. He was at first treated in London, but after being cared for by his sister and brother-in-law, he moved to the Velindre Cancer Centre in Whitchurch for radiotherapy treatment. He died from the disease at Monnow Vale Community Hospital in Monmouth on the morning of 18 June 2012, as announced by his agent.