English painter and printmaker.

Riley studied in London at Goldsmiths College (1949-52) and the Royal College of Art (1952-5). From 1958 to 1959 she worked in an advertising agency while painting in a pointillist technique. She was encouraged in this by her teacher, the painter Maurice de Sausmarez (d 1970), who directed her to study the art of Seurat.

Her interest lay in the energy and colour vibrations radiated by objects, which indirectly led to her experimentation with and eventual pioneering of so-called Op Art. The term Op Art was used as an abbreviation of 'optical art', which referred to painting and sculpture that exploits the illusions or optical effects of perceptual processes. It was used for the first time by a writer in an unsigned article in Time magazine (23 Oct 1964) and entered common usage to designate, in particular, two-dimensional structures with strong psychophysiological effects.

Other outstanding Op artists included Victor Vasarely, Jesús Soto, Julio Le Parc and François Morellet. The Hayward Gallery held a major exhibition of her work in 1992 and the Tate Gallery and British Council, amongst others, hold her work.

New Paintings, New Gouaches, 25- May - 30 June 2007, Green on Red Gallery, Dublin