O'Neill, Daniel (1920–74), landscape and portrait artist, was born 21 January 1920 in Belfast, the eldest of one son and two daughters of Frank O'Neill, an electrician, of 4 Dimsdale St., and Mary O'Neill. He was educated at St John's public elementary school in Clonard St., and then trained as an electrician. Though he attended evening classes in the art department of the Belfast College of Technology in 1939, and worked for a short time in the studio of Sidney Smith, he was ultimately a self-taught artist. An electrician in the Belfast Corporation transport department, he worked the night shift and painted during the day; later he worked in the Belfast shipyards. In 1940 he met the painter Gerard Dillon (qv), who introduced him to the work of artists such as Cézanne and Picasso; together they carved images on stones retrieved during the wartime blitz in Belfast. O'Neill participated in a small group show at the Mol Gallery, Belfast, in 1940, where none of his eleven works was sold. In 1943 he held a joint exhibition with Dillon at the Contemporary Picture Galleries, Dublin, showing ‘Head of a clown’, an early work expressing the influence of Rouault, and religiously inspired paintings such as ‘Madonna’ and ‘Head of Christ’. Owing to the high cost of canvas during the second world war, he experimented with many materials, such as cardboard, tablecloths, and plywood. A reproduction of his painting ‘Conlig Street’ was printed in Now in Ulster (1944), an anthology of prose and verse; in the same year he first exhibited at the Irish Exhibition of Living Art.
In 1945 he met the art dealer Victor Waddington, who encouraged him to paint full-time, offered him a gallery contract, and provided him with his first solo exhibition (Dublin, 1946), thereby establishing his reputation. In 1947 O'Neill showed works in New York, and exhibited a painting entitled ‘Madelaine’ at the RHA, where he exhibited nearly every year until 1957. His paintings were included in the progressive ‘Nine painters’ exhibition (1947), held in the Belfast gallery of CEMA (Council for the Encouragement of Music and the Arts). He participated with Dillon, George Campbell (qv), and Neville Johnson (1911–99) in the ‘Four Ulster artists’ show at Heal's Mansard Gallery, London (1948). His painting ‘The blue skirt’ (1949) marked an innovative departure for Northern Irish painting in its invocation of the European tradition. Visiting Paris in 1949, he painted ‘Place du tertre’, a work capturing a sense of the bohemian nightlife of the Montmartre district. In 1950 his work was included in an exhibition of Irish religious paintings in the Ashley Gallery, London, and in an exhibition of Irish art that toured the USA and Canada; the latter included his painting ‘Artist and models’.
During these years O'Neill was living in Conlig, Co. Down, where he was often joined by Campbell and Dillon, who painted with him. O'Neill also painted in the Rathmullen area of Co. Donegal; ‘Knockalla hills, Donegal’ typifies his expressionist style. His painting ‘The first born’ (1949), shown at the Victor Waddington Gallery, Dublin, evoked a sensuous vision of motherhood through its romantic and primitive expression. One of his most impressive paintings, ‘Birth’ (1952), depicted a highly dramatic scene, attained through swift brushstrokes and use of the palette knife; the figure of the small boy is O'Neill himself. He exhibited paintings in the 1950 Irish Exhibition of Living Art in Dublin, and was a member of the organising committee. He showed ‘Gamekeeper’ at a collaborative exhibition, ‘Five Irish painters’, at the Arthur Tooth Gallery, London (1951). Forty-five of his paintings, redolent of his emotional, sensuous use of colour, were shown at a major retrospective loan exhibition in the Belfast Museum and Art Gallery in 1952, sponsored by CEMA. He designed sets for the Abbey Theatre's 1957 production of ‘The playboy of the western world’ by J. M. Synge (qv). In 1958, the year that he moved to London, O'Neill showed paintings at the Waddington Galleries, Montreal, Quebec, Canada. He held one-man shows in the Dawson Gallery, Dublin, in 1960 and 1963. In 1969 in Belfast he met George McClelland, who became his dealer and supplied him with a place to live for four years. At the McClelland Galleries in 1970 O'Neill made a huge impact with his first one-man show in Belfast for eighteen years.
O'Neill and his wife Eileen married in 1942; they had one daughter. ‘Donegal couple’ (n.d.), a self-portrait with his wife, was painted before their divorce in 1960. Described as ‘the finest Irish romantic painter after Jack Yeats’ (Ir. Times, 12 Mar. 1974), O'Neill was a brooding artist, who, in his early paintings, which were inspired by the blitz and by post-war Belfast, expressed a soulful, sometimes disturbing melancholy that was a pervasive aspect of his own personality. His portraits, particularly those of women, evoked an emotional fusion between colour, mood, and illusion. He returned to live in Belfast in 1971, but his paintings had lost their original vigour, and predicted an artist in crisis. When the McClelland Galleries were destroyed by a bomb in 1971 he lost his main outlet; his studio and flat were also lost in a fire. He died suddenly 9 March 1974 at the City Hospital, Belfast, and was buried in Milltown cemetery. An exhibition of selected figurative works by O'Neill, held in the Octagon Gallery, Belfast, in 1987, traced his developing modernist style, especially in the years he was absent from Belfast.