Sir Polydore de Keyser (13 December 1832 – 14 January 1898), was a lawyer and the first Roman Catholic since the Reformation to be elected Lord Mayor of London (October 1887 – November 1888).
De Keyser belonged to several different City companies (Spectacle Makers, Farriers, Butchers, Innholders, Poulterers, Gold and Silver Wire Drawers) and was a governor of Bridewell, Bethlem and St. Bartholomew's hospitals.
De Keyser served as Sheriff of London and Middlesex 1882–83 and was elected alderman to represent Farringdon Without on the Court of Common Council.
(Welkom der Stad Brussel aan den Hoogachtbaren Heer Polydoor De Keyser, Lord-Major van Londen and Heilgroet aan den Hoogachtbaren Heer Polydoor De Keyser, Lord-Major van Londen, in zijn vaderstad Dendermonde).
The De Keyser's Royal Hotel had approximately 400 rooms and was mostly used by foreigners visiting London, including Americans, Dutch, French and Belgians.