Sir Nicholas Bacon (28 December 1510 – 20 February 1579) was Lord Keeper of the Great Seal during the first half of the reign of Queen Elizabeth I of England. He was the father of the philosopher and statesman Sir Francis Bacon.

He was born at Chislehurst, Kent, the second son of Robert Bacon (1479–1548) of Drinkstone, Suffolk, by his wife Eleanor (Isabel) Cage.

He graduated from Corpus Christi College, Cambridge in 1527. The college law society at Corpus, the Nicholas Bacon Law Society, founded in 1972, is named after him.

There is a story that he evaded ordination by going into hiding "with the help of a rich uncle", and he seems to have entered an Inn of Chancery before being admitted to Gray's Inn five years later after a period in Paris; he was called to the Bar in 1533.

Following the Dissolution of the Monasteries, Henry VIII gave him a grant of the manors of Redgrave, Botesdale and Gislingham in Suffolk, and Gorhambury, Hertfordshire. Gorhambury belonged to St Albans Abbey and lay near the site of the vanished Roman city of Verulamium (modern day St Albans). From 1563 to 1568 he built a new house, Old Gorhambury House (now a ruin), which later became the property of Francis Bacon, his youngest son, who also built a nearby property, Verulam House, to his own designs.

In 1545 he became a Member of Parliament, representing Dartmouth. The following year, he was made Attorney of the Court of Wards and Liveries, a prestigious and lucrative post, and by 1552 he had risen to become treasurer of Gray's Inn.

As a Protestant, he lost preferment under Queen Mary I of England. However, on the accession of her younger sister Elizabeth in 1558, he was appointed Lord Keeper of the Great Seal, largely owing to the influence of his brother-in-law William Cecil. Shortly afterwards, Bacon was knighted.

Bacon helped secure the position of Archbishop of Canterbury for his friend Matthew Parker, and in his official capacity presided over the House of Lords when Elizabeth opened her first parliament. Though an implacable enemy of Mary, Queen of Scots, he opposed Cecil's policy of war against France, on financial grounds; but he favoured closer links with foreign Protestants, and was aware of the threat to England from the alliance between France and Scotland. In 1559 he was authorized to exercise the full jurisdiction of Lord Chancellor. In 1564 he fell temporarily into the royal disfavour and was dismissed from court, because Elizabeth suspected he was concerned in the publication of a pamphlet, A Declaration of the Succession of the Crowne Imperial of Ingland, by John Hales, which favoured the claim of Lady Katherine Grey (sister of Lady Jane Grey) to the English throne.