Sir Lewis Thomas Casson MC (26 October 1875 – 16 May 1969) was a British actor and theatre director, and the husband of actress Dame Sybil Thorndike.
Lewis Casson was born at 18 Alfred Road, Birkenhead, Cheshire. He was the son of a bank manager and amateur organ-builder, Thomas Casson, from Wales, and his wife Laura Ann. When he was young the family moved to Denbigh in Wales and Casson was educated at Ruthin School. In 1891 Casson's father decided to make a business of his hobby of building organs, and the family moved to London. Lewis soon began working in his father's business. When this failed, he began to study chemistry, but then trained as a teacher at St Mark's College, Chelsea, where he gained a teaching certificate. In 1900 Casson's father began another organ making business and Lewis worked in this for the next four years.
Casson had always been interested in acting and had taken part in amateur productions in his youth. He continued to act semi-professionally until 1904, when he left his father's business to work as a professional actor. He joined the Royal Court Theatre under Harley Granville-Barker and remained there until 1908, when he joined a repertory company founded by Annie Horniman at the Gaiety Theatre in Manchester, the first repertory theatre in the country.
On 22 December 1908, in Aylesford, Kent, he married Sybil Thorndike, who was another member of the company. They both joined Charles Frohman's repertory season in London. In 1909 Sybil gave birth to their first son, John, and soon after, they joined Frohman on a tour of the United States. When Casson returned to England he became a theatrical director working with Annie Horniman from 1911-13. He then succeeded Alfred Wareing as the producer of the Scottish Playgoers Company, based in Glasgow, and forerunner of the Citizens' Theatre, in which his elder son John would become an actor-director. In 1912, a second son, Christopher, was born.