Sir Walter Mildmay (bef. 1523 – 31 May 1589) was an English statesman who served as Chancellor of the Exchequer of England under Queen Elizabeth I, and was founder of Emmanuel College, Cambridge.
Born at Moulsham, Essex, Mildmay was the fourth and the youngest son of Thomas Mildmay, Auditor of the Court of Augmentations for Henry VIII, by his wife, Agnes Read. As the Commissioner for receiving the surrender of the monasteries, his father Thomas had made a large fortune and in 1540 was granted the Manor of Moulsham, near Chelmsford, where he built a fine mansion.
Mildmay was educated at Christ's College, Cambridge, but apparently failed to take his degree. He later became a student of law at Gray's Inn (1546), and there obtained some employment under his father in the Court of Augmentation.
When the Court of Augmentation was reconstituted, about 1545, Mildmay was made one of its two surveyors-general. During Edward VI's reign, Mildmay extended his official connection. On 22 February 1546-7 he was knighted, and on 14 September prepared, along with three others, an inventory of the late King's wardrobe. Sixteen days later he was appointed a Commissioner to report upon the Crown revenues. In 1548 he acted on commissions for the sale of lands (March) and for the maintenance of such grammar schools as had belonged to the dissolved chantries. After the Duke of Somerset's arrest he was ordered by the Privy Council on 12 November 1549, to examine the royal palace at Westminster, which had been in the Duke's custody, and on 8 March 1550-1 to take charge of the Duke's property at Syon House.