Lieutenant General Sir William Nicolay KCH CB (14 April 1771 – 3 May 1842) was a British Army officer present at the Battle of Waterloo who later became Governor of Mauritius.
He was the third son of Frederick de Nicolay, Principal Page to Princess Charlotte of Mecklenburg-Strelitz, wife of King George III. He was born at St. James's Palace on 14 April 1771 and was a member of the British branch of the Nicolay family.
He entered the Royal Military Academy, Woolwich, as a cadet on 1 Nov. 1785, but did not obtain a commission as second lieutenant Royal Artillery until 28 May 1790. In April 1791 he embarked for India with two newly formed companies of Royal Artillery, known as the ‘East India Detachment,’ which subsequently formed the nucleus of the old sixth battalion (Duncan, Hist. Roy. Artillery, ii. 2).
He served under Lord Cornwallis at the siege of Seringapatam in 1792, and was an assistant engineer at the reduction of Pondicherry in 1793. Meanwhile, with some other artillery subalterns, he had been transferred in November 1792 to the Royal Engineers, in which he became first lieutenant on 15 August 1793 and captain on 29 August 1798. He was present at the capture of Saint Lucia, and was left there as commanding engineer by Sir John Moore. He afterwards served under Sir Ralph Abercromby at Tobago and Trinidad until compelled to return home by a broken thigh, which incapacitated him for duty for two years.