Lucy Thomas (née Williams, baptised 11 March 1781 – 27 September 1847) was a Welsh businesswoman and colliery owner known as the "mother of the Welsh steam coal trade". Thomas took over the running of her husband Robert's coal mine after his death in 1833. Unusual as it was at the time that a woman ran the business, more unusually she was also illiterate. Business documents held in the Glamorgan Archives show she signed only with an X. Much of Thomas' subsequent success as a businesswoman was embellished by Merthyr historian Charles Wilkins, who wrote one of the few articles on her life in 1888. It is now believed that George Insole, a Cardiff agent, was one of the chief architects of her success, though this does not diminish Thomas' position as one of the few women coal owners in industrial Britain. It is recorded that Lucy once attended the Coal Exchange in Cardiff only to be told she could not enter. She sent a male clerk in her employ into the Coal Exchange with a letter informing the establishment that 'My coal is equal to any mans, failure to grant entry will lead to my business lining another's pockets'.