Sir William Johnston Thomson MIME (1881–1949) was a Scottish engineer and businessman involved in the early automobile industry. He served two consecutive terms as Lord Provost of Edinburgh from 1932 to 1935. He established the first city-to-city bus services in Scotland.

Thomson was born in 1881 to a Caithness family.

He served his apprenticeship as an engineer at J & T Boyd, manufacturers of textile-making machines at Shettleston Ironworks in Glasgow.^[1] Around 1899 he joined the firm Pollock, McNab & Highgate based at Carntyne Station in Shettleston. Around 1900 he joined the newly created automobile manufacturer Arrol-Johnston.

In 1905 Thomson founded the Scottish Motor Traction Company (known as the SMT) which began operations at 9 Lauriston Street in south-west Edinburgh in 1906. In 1929 the company took over W. Alexander & Sons, its main rival, together with smaller Scottish bus companies, and thereafter had a near monopoly on public transport provision in central Scotland. In conjunction with LMS and LNER, the SMT group controlled most rail and road freight.^[2][3]

In 1932 he succeeded Thomas Barnby Whitson as Lord Provost of Edinburgh. At the end of his term of office, as was customary, he received a knighthood from George V. However, he then continued for a further term until 1935.^[4] He was succeeded by Louis Stewart Gumley.^{[citation needed]}

Thomson died on 18 September 1949.