Thomas was born and raised in Swansea, Wales, where he was a poor student. He dropped out of school at age 16 and became a newspaper reporter. Before he turned 20, he won a newspaper poetry contest. His first book, Eighteen Poems, was published in 1934, followed by Twenty-five Poems in 1936.
At age 21, Thomas moved to London, where he met Caitlin Macnamara in a pub. Although the lively Irish girl did not initially find him attractive, his charm won her over, and the pair married the following year, the beginning of a long, tumultuous, and ultimately unhappy marriage.
Despite the couple's domestic turmoil, they had three children. Meanwhile, Thomas published several highly acclaimed books, including Deaths and Entrances in 1946 and Collected Poems in 1953. His powerful style, combining compassion and violence, made his readings in the United States a success. However, during his tours, he drank recklessly. In 1953, he collapsed after drinking 17 whiskeys at the White Horse Inn on Hudson Street in New York City and died at age 39.