Sir Louis Mallet (1823 – 16 February 1890, Bath) was a British civil servant. He was Permanent Under-Secretary of State for India.
He was born in London and was in all probability educated there, though at which school or college is not known. He began his career in the Civil Service as a clerk in the Audit Office and appears to have initially had nothing to do with India. He would have gained a certain amount of experience in matters commercial, as he was Private Secretary to the President of the Board of Trade between 1848-1852 and between 1855-1857. In his official career, he does not appear to have dealt directly with India until 1872, rather dealing with commercial matters, as Assistant Commissioner for a Trade Treaty with France 1860-1865 and then again for a similar Treaty with Austria 1865-1867.
In 1872, he was appointed to the Council of India, where he remained until 1874, being appointed during that year as the Permanent Under-Secretary of State for India, a position left vacant by the death of the incumbent Sir Herman Merivale. He remained there until his retirement in 1883, touring India in 1875-1876, which was facilitated by the opening of the Suez Canal in 1869. After retirement, he represented India at a Monetary Conference held in Paris in 1887, while his knowledge of matters commercial was put to use as a member of the Royal Commission on Precious Metals also constituted in 1887.
In 1858 he married Frances Helen Pellew, and they had four children, all being sons. His mother's name was Frances Merivale; he was in fact a first cousin of his predecessor at the India Office. His major publication was Free Exchange, which came out in 1891, after his death.
His son was Sir Bernard Mallet.