William Lawson, MLC (2 June 1774 – 16 June 1850) was a British soldier, explorer, land owner, grazier and politician. In 1800, he migrated to Sydney, New South Wales, and from 1819, he served as the commandant of the Bathurst, New South Wales region, and from 1843, he served as a member of the New South Wales Parliament.

In 1813, Lawson pioneered the first successful crossing of the Blue Mountains by British colonists, along with Gregory Blaxland and William Wentworth, and they discovered inland pastures that fuelled the colony's economic growth thereafter.

Lawson was born in Finchley, Middlesex, England. He was the son of John Lawson and his second wife Hannah Summers. His father owned a successful chandler business, and he was a descendant of the Scottish Lawson family of Cairnmuir House in the Pentland Hills of Edinburgh, Scotland.

Lawson was educated in London and trained as a surveyor. He decided to join the British Army and purchased a commission in the New South Wales Corps as an ensign for £300 in 1799. He received orders to transfer to Sydney, arriving there in November 1800.

Shortly after his arrival in Sydney he was posted to work at the penal colony at Norfolk Island under Major Joseph Foveaux. At this time, a planned insurgency of Irish convicts and soldiers on the island was discovered with Foveaux hanging two alleged ring-leaders without trial and punishing others with 500 lashes. Lawson became trusted by Foveaux and was appointed to adjudicate in the island's military court. This court was accused of corrupt practices and in one high profile case which Lawson helped preside over, an appointee to a government position who Foveaux did not like was found guilty of incest.

In addition to his military duties on Norfolk Island, Lawson also acquired land and raised sheep. He also obtained a convict mistress named Sarah Leadbeater, who had been sentenced to 7 years transportation for stealing clothes. He developed a long term relationship with Sarah, eventually marrying her in 1812 and having eleven children with her.

In 1806, Lawson returned to Sydney and was promoted to the rank of lieutenant in the New South Wales Corps. Here he became a close associate with the leading officers including Captain John Macarthur and Lieutenant-Colonel George Johnston. These officers controlled a very profitable monopoly in the colony that centred on the trading on rum, and the New South Wales Corps was called the 'Rum Corps' as a result of this corrupt racketeering. Lawson became an integral part of this clique.

In January 1808, when Governor Bligh had John Macarthur arrested on charges of sedition against the colonial government, Lawson was one of six officers appointed to help oversee his trial. Colluding with Macarthur, Lawson and the other officers refused to acknowledge the legitimacy of the presiding judge, took possession of the court documents and removed Macarthur from the custody of the court. When Bligh ordered Lawson and the other officers to halt their interference in the trial, they refused, resulting in Bligh charging them with treason. Macarthur, Johnston, Lawson and the other officers and soldiers of the 'Rum Corps' then proceeded to collaborate in a full armed mutiny against Governor Bligh known as the Rum Rebellion. This military coup resulted in the detainment and removal of Bligh from power, and the installation of a military junta headed by Macarthur and Johnston.