Sir Ernest Ridley Debenham, 1st Baronet (26 May 1865 – 25 December 1952), was an English businessman. He was responsible for the considerable expansion of the family's retail and wholesale drapery firm between 1892 and 1927.
Born at 42 Wigmore Street, Marylebone, he was the son of Frank Debenham and his wife Emma Folkard née Ridley. Educated at Marlborough College and Trinity College, Cambridge, At the age of 27 he joined the successful business of Debenham & Co., which had been run by his grandfather and father. His restructuring activities led to the splitting of the manufacturing from the retail side of the business, under the name Debenham & Freebody (Freebody was the maiden name of his grandmother). He effected a merger with Marshall & Snelgrove as well as a takeover of Harvey Nichols. He was noted for his paternalistic attitude towards his staff, providing medical and educational support. He was also a pioneer in the dairy industry.
Debenham had an interest in politics, and was a supporter of the Conservative Party. Although he considered entering parliament his business interests prevented this. He did enter local politics however. He was a member of St Marylebone Borough Council, serving as mayor of the borough in 1910-12.  He was also a member of the London County Council. He was elected unopposed at a by-election on 28 February 1912 for the Conservative-backed Municipal Reform party to represent the Marylebone East division, remaining a councillor until 1919.
On his retirement in 1927 he sold most of his shares in the firm for £1.8M, so severing his family's connections with the retail chain that still bears his name. He devoted the rest of his life to dairy farming on his estates in Dorset. He was created a baronet, of Bladen in the County of Dorset, in 1931. He died on Christmas Day 1952 at Moor Lane House, Briantspuddle, Dorset, and was succeeded in the baronetcy by his son, Piers Kenrick Debenham, born in 1904. 
- "Obituary: Sir E. R. Debenham". The Times. 29 December 1952. p. 8.
- Shaw, Gareth (2004). "Debenham, Sir Ernest Ridley, first baronet (1865–1952), department store owner". Oxford Dictionary of National Biography. Retrieved 8 June 2014.
- "Debenham, Ernest Ridley (DBNN883ER)". A Cambridge Alumni Database. University of Cambridge.
- "Election of Mayors". The Times. 10 November 1910. p. 8.
- "Election of Mayors". The Times. 10 November 1911. p. 7.
- The London Gazette: . 3 February 1931.
|Baronetage of the United Kingdom|
Piers Kenrick Debenham