James Robert Martin (born 1950) is a Canadian-born linguist based at the University of Sydney, where Michael Halliday recruited him to the newly founded Linguistics Department in 1977. He holds a Personal Chair as Professor of Linguistics and is the principal theorist behind the so-called Sydney School of systemic functional linguistics, the branch of post-Hallidayan SFL that pushed the theory outwards into discourse semantics, genre, appraisal, and school literacy.
Martin writes like someone who refuses to let a social theory of language stop at the clause. His contribution has been to stratify the content plane above lexicogrammar, treat register and genre as distinct semiotic layers, and give teachers a working account of how whole texts mean. The result is a theory thick enough to describe a science report and practical enough to teach one.