Sebastian Patrick Quintus Rahtz (13 February 1955 – 15 March 2016) (SPQR) was a British digital humanities information professional.

[1][2] Born in 1955 to archaeologist Philip Rahtz, Sebastian also trained in archaeology, and was awarded a PhD in 1974 from University College London.

[4] Rahtz was a long-term contributor to several communities in the broader digital humanities, including LGPN, TeX,[5][6] computer methods in archaeology,[7] and the Text Encoding Initiative (TEI).

[8] Sebastian's legacy also includes the vital contributions which he made to building and maintaining much of the TEI's technical Infrastructure and related software such as their XSLT stylesheets and web-based document conversion engine OxGarage,[9] CLAROS,[10] the Oxford Text Archive,[11] Text Creation Partnership[12] and OSS Watch.

In September 2016, Oxford University ran a whole-day event celebrating his life, with speakers talking about his projects.