Lewis Edward Valentine (1 June 1893 – March 1986) was a Welsh politician, Baptist pastor, author, editor, and Welsh-language activist.
Valentine was born in Llanddulas, Conwy, the son of Samuel Valentine, a limestone quarryman, and his wife Mary. He began studying to go into the ministry of the Baptist church at the University College of North Wales, Bangor but his studies were curtailed due to the First World War.
His experiences in World War I, and his sympathy for the cause of Irish independence, brought him to Welsh nationalism, and in 1925 he met with Saunders Lewis, H. R. Jones, and others at a 1925 National Eisteddfod meeting, held in Pwllheli, Gwynedd, with the aim of establishing a Welsh party.
Discussions for the need of a "Welsh party" had been circulating since the 19th century. With the generation or so before 1922 there "had been a marked growth in the constitutional recognition of the Welsh nation," wrote historian Dr. John Davies. By 1924 there were people in Wales "eager to make their nationality the focus of Welsh politics".
The principal aim of the new party would be to foster a Welsh speaking Wales. To this end it was agreed that party business be conducted in Welsh, and that members sever all links with other British parties. Valentine, Lewis and others insisted on these principles before they would agree to the Pwllheli conference.
According to the 1911 census, out of a population of just under 2.5 million, 43.5% of the total population of Wales spoke Welsh as a primary language. This was a decrease from the 1891 census with 54.4% speaking Welsh out of a population of 1.5 million.