Prince Frederick Augustus, Duke of York and Albany (16 August 1763 - 5 January 1827) was the second son of King George III of the United Kingdom and Queen Charlotte. From 1817 until his own death in 1827, he was the heir presumptive to his elder brother, King George IV. As the commander-in-chief of the British Army, he presided over the unsuccesful 1793-98 Flanders campaigns during the French Revolutionary Wars. He is now mainly remembered as the inspiration for the nursery rhyme, "The Grand Old Duke of York".

His Royal Highness Field Marshal The Prince Frederick Augustus, Duke of York and Albany, Earl of Ulster, KG, PC, GCB, GCH, was born at St. James's Palace, London. When Prince Frederick was six months old, his father secured his election as Prince-Bishop of Osnabrück in Lower Saxony. He was invested as Knight Grand Cross of the Most Excellent Order of the Bath in 1767 and as a Knight of the Order of the Garter on 19 June 1771.

George III decided that his second son would pursue an army career and had him gazetted colonel in 1780. From 1781 to 1787, Prince Frederick lived in Hanover, where he attended the manoeuvres of the Austrian and Prussian armies and studied (along with his younger brothers, Prince Ernest, Prince Edward, Prince Augustus and Prince Adolphus) at the University of Göttingen. He was appointed colonel of the 2nd Horse Grenadier Guards (now 2nd Life Guards) in 1782, and promoted major-general and appointed colonel of the Coldstream Guards in 1784. He was created Duke of York and Albany and Earl of Ulster on 29 November 1784 and became a member of the Privy Council. He retained the bishopric of Osanbrück until 1803, when, in the course of the secularization preceding the dissolution of the Holy Roman Empire, the bishopric was incorporated into Hanover. On his return to Britain, the Duke took his seat in the House of Lords, where, on 15 December 1788, he opposed William Pitt's Regency Bill in a speech which was supposed to have been inspired by the Prince of Wales.

The Duke of York was his father's favorite son. He was very much in the shadow of his elder brother, the Prince of Wales, especially when the latter became Prince Regent. However, the two brothers enjoyed a close relationship.

On 29 September1791 at Charlottenburg, Berlin, and again on 23 November 1791 at Buckingham Palace, the Duke of York married his cousin Princess Frederica (7 May 1767 - 6 August 1820), the daughter of King Frederick William II of Prussia and Princess Elizabeth of Brunswick-Wolfenbüttel. The new Duchess of York received an enthusiastic welcome in London, but the marriage was not a happy one. The couple soon separated and the Duchess retired to Oatlands Park, Weybridge, where she died in 1820. The Duke and Duchess of York had no children. The Duke's only known child was an illegitimate son, Charles Hesse, and even this is uncertain.

In 1793, the Duke of York was sent to Flanders in command of the British contingent of Coburg's army destined for the invasion of France. On his return to Britain in 1795, George III promoted him to the rank of field marshal, and on 3 April 1798, appointed him commander-in-chief in succession to Lord Amherst. His second field command was with the army sent to invade Holland in conjunction with a Russian corps d'arm in 1799. Sir Ralph Abercromby and Admiral Sir Charles Mitchell, in charge of the vanguard, had succeeded in capturing the Dutch ships in the Helder. However, following the Duke of York's arrival with the main body of the army, a number of disasters befell the allied forces. On 17 October, the Duke signed the convention of Alkmaar, by which the allied expedition withdrew after giving up its prisoners.

His military failures led to his immortalisation in the rhyme:

The grand old Duke of York,
He had ten thousand men.
He marched them up to the top of the hill
And he marched them down again.

However, he carried out many reforms in the army which would lead to subsequent successes in the Napoleonic Wars. He resigned as commander-in-chief of the army on 25 March 1809 as a result of a scandal caused by the activities of his mistress, Mary Anne Clarke. A select committee appointed by the House of Commons to inquired into the matter. The full House aquitted the Duke of having received bribes by 278 votes to 196. Two years later, on 29 May 1811, the Prince Regent reappointed the Duke of York commander-in-chief, a post he held until his death, and created him Knight Grand Cross of the Royal Guelphic Order.

Following the death of his niece Princess Charlotte of Wales in 1817, the Duke of York was heir presumptive to the throne. However, he pre-deceased his elder brother, George IV, dying at the home of the Duke of Rutland on Arlington Street, London. He was buried at St. George's Chapel, Windsor.