Born in St Ives, a location which would become his favourite subject and source of inspiration throughout his career, Lanyon was educated at St. Erbyn's School, Penzance and Clifton College, Bristol. Upon leaving Clifton College he received drawing lessons from Borlase SMART.

In 1937 he met Adrian STOKES, the writer, who encouraged him to enroll at Euston Road School in London in 1938 (where he was taught by William Coldstream and Victor PASMORE) and who also introduced him to Ben NICHOLSON, Barbara HEPWORTH and Naum GABO.

He became a pupil at Leonard John FULLER 's St Ives School of Painting, and then served in RAF during WWII. After his return to Cornwall he bought Little Parc Owles, which Stokes had vacated, and married Sheila St John Browne in 1946. Increasingly inspired by his surrounding Cornish landscape, he contributed work to many exhibitions and shows in St Ives.  

His paintings reflected people and buildings in landscape, but were also inspired by the weather, ancient myths and evidence of modern industries that abound in the landscape. By the 1950s he was recognized as a leading member of St Ives Group, and was a Founder member of the Penwith Society of Arts in Cornwall when it emerged in 1949.  His first one-man exhibition was held at the Lefevre Gallery in London, and in his review of the show, Patrick HERON commented on the restriction he felt Lanyon imposed on himself in his most abstract designs.

Lanyon began teaching at the Bath Academy of Art, Corsham (1950-1957), where William SCOTT was senior painting master, and was invited by the Arts Council to participate in the 1951 Festival of Britain Touring exhibition.  In the St Ives art scene, Lanyon had a serious dispute with Nicholson regarding the latter's intention to divide the Penwith Society of Artists into two categories: figurative and non-figurative, firmly believing the distinction to be false.

In 1953 he spent four months in Italy on an Italian government scholarship. In the same year, he was elected to the Newlyn Society of Artists (NSA). In 1954 he was awarded Critic's Prize by the British section of the International Association of Art Critics.

Lanyon ran an art school, St. Peter's Loft, at St Ives with Terry FROST and William REDGRAVE between 1957-60, and mounted his first solo exhibition in New York at the Catherine Viviano Gallery (1957), meeting Rothko, Motherwell and other important members of the American art world. He found there a freer approach which allowed for a new lively and spirited style for him.  In 1959 he was awarded Second Prize in the John Moores Exhibition, Liverpool. 

At around this time he began gliding to get, as he explained, 'a more complete knowledge of the landscape'.  He also took up the Chairmanship of the NSA (1961), and was elected Bard of Cornish Gorsedd for services to Cornish art.

In 1964 he visited Prague and Bratislava to lecture for the British Council, and was considerably impressed by the lively cultural and artistic scene which he found behind the Iron Curtain. Lanyon died tragically and unexpectedly as a result of injuries sustained during a gliding accident on 31 August at Taunton. Great interest and respect for his work has remained to the present day in Cornwall and internationally, celebrated in a major Retrospective at Tate St Ives during Winter 2010/11.