Marsden, Alexander (1761–1834), barrister, East India Company agent, and government official, was born in Dublin, probably in October 1761 – he was baptised at St Michan's, Dublin, on 17 October – the youngest of the sixteen children of John Marsden (1716?–1801) and his second wife, Eleanor (d. 1804), daughter of Alexander Bagnell of Edinburgh. John Marsden, a merchant with interests in shipping, had houses at Lazer's Hill and Clontarf and an estate at Vervale, Co. Wicklow, and was a director of the Bank of Ireland (1784–97). Alexander Marsden's grandfather Edmund Marsden (1664–1724), said to be a carpenter, had arrived in Dublin from Baslow, Derbyshire, and acquired property.
After entering TCD (2 November 1778), Marsden graduated BA (1783) and LLB (1786). He was admitted to Lincoln's Inn, London, on 19 January 1785 and called to the Irish bar in 1787; from 1789 he was listed in Wilson's Dublin Directory with an address in Harcourt Street (until 1795) and then Baggot Street (1796–1802). According to the family history, however, he joined his brother William (qv), who, having served the East India Company, returned from Bencoolen with his savings (1779) and, with another brother, John (1745–86), a writer at Bencoolen, set up an East India agency in Gower Street, London (January 1785). As John died 13 April 1786 at Bencoolen, it seems likely that Alexander saw and seized a business opportunity in London. At dates not known he traded at 76 Lombard Street as Alexander Marsden & Co. It may be presumed that by 1789 this venture was over.
Marsden's election on 22 January 1787 to membership of the RIA suggests that he was in Dublin on that date. Owing to the influence of Edward Cooke (qv), he took up (in 1798) a post at Dublin Castle which seems to have been created for him – assistant secretary in the law department in the chief secretary's office. He made himself useful beyond his remit. The lord chancellor, the earl of Clare (qv), however, thought him ‘a little pettifogger’. On 21 October 1801 he was appointed under-secretary to Cooke, a position he turned into a powerful one owing to the deference of the lord lieutenant, the earl of Hardwicke (qv). He did not, however, prevent the uprising led by Robert Emmet (qv), though he had been forewarned, and so was criticised. When he left office (1806) he was widely unpopular. The Dublin common council voted 42 to 22 against an address of thanks for his conduct in office – he had promoted a Dublin police bill. But even opponents on the council credited him with ‘urbanity and politeness’.
Marsden's next appointment was as a commissioner of a new board of excise (September 1806), of which he became chairman (1810), retiring in 1815. After the creation of the civil list (1806) he was given a pension of £300 p.a. Towards the end of his life (1822?) Marsden moved to London and resided in Portland Place. He died 22 September 1834 and was buried at Kensal Green. His marriage (3 July 1794) to Elizabeth Cooper, daughter of John Cooper (d. 1808) of Cooper Hill, Co. Meath, resulted in three daughters.