George I (Georg Ludwig von Hanover) (May 28, 1660–June 11, 1727) was Duke of Brunswick-Lüneburg (Hanover) from January 23, 1698, and King of Great Britain and King of Ireland from August 1, 1714, until his death in 1727.

He was also the Archbannerbearer (afterwards Archtreasurer) and a Prince Elector of the Holy Roman Empire. George I, the first Hanoverian monarch of Great Britain and Ireland, was not a fluent speaker of the English language; instead, he spoke his native German, and was for this ridiculed by his British subjects.

During his reign, the powers of the monarchy found themselves diminished; the modern system of government by a cabinet underwent development. During the later years of his reign, actual power was held by a de facto Prime Minister, Sir Robert Walpole.

George's mother, the Electress Sophia, died only a few weeks before Anne, Queen of Great Britain. Pursuant to the Act of Union 1707, George became King of Great Britain when Anne died on August 1, 1714. He did not arrive in Great Britain until September 18th; during his absence, the Lord Chief Justice of the King's Bench acted as a regent. He was crowned at Westminster Abbey on October 20th.

Upon his accession in Great Britain, George established a firm practice relating to the dignity of princes. Before the Hanoverians, the only princely dignities were those of Prince of Wales (customarily granted to the heir-apparent) and Princess Royal (customarily granted to the sovereign's eldest daughter).

The other members of the Royal Family were only entitled to the styles "Lord" and "Lady." George I, however, was accustomed to the German practice, whereunder the princely dignity was more common. Consequently, the sovereign's children and grandchildren in the male line became princes and princesses styled "Royal Highness," and great-grandchildren in the male line became princes and princesses styled "Highness."

George I primarily resided in Great Britain, though he often visited his home in Hanover. During the King's absences, power was vested either in his son, George, Prince of Wales, or in a committee of "Guardians and Justices of the Kingdom." Even while he was in Great Britain, the king occupied himself with Hanoverian concerns. He spoke poor English, and many of his contemporaries thought him unintelligent. Power consequently passed from the Crown to its ministers.

In 1715, when not even a year had passed after George's accession, he was faced with a Jacobite Rebellion, which became known as "The Fifteen." The Jacobites sought to put Anne's Catholic brother, James Francis Edward Stuart (whom they called "James III", and who was known to the English as the "Old Pretender") on the throne. The Old Pretender instigated rebellion in Scotland, where support for Jacobitism was stronger than in England.

John Erskine, 6th Earl of Mar, an embittered Scottish nobleman who had previously supported the Glorious Revolution, led the rebels. The Fifteen, however, was a dismal failure; Lord Mar's battle plans were poor, and the Old Pretender had not arrived in Scotland in time. By the end of the year 1715, the rebellion had all but collapsed. Faced with impending defeat, Lord Mar and the Old Pretender fled to France in the next February. After The Fifteen was crushed, the British government dealt with the insurgents harshly. Several prisoners were executed; the remainder were enslaved in the colonies. Numerous Scottish noble families lost their estates.

Several members of the Tory Party sympathized with the Jacobites. George I began to distrust the Tories, and power thus passed to the Whigs. Whig dominance would be so great under George I that the Tories would not return to power for another half-century. As soon as the Whigs came to power, Parliament passed the Septennial Act, which extended the maximum duration of Parliament to seven years (although it could be dissolved earlier by the sovereign). Thus, Whigs already in power could remain in such a position for a greater period of time.

George I, although increasingly reliant on Sir Robert Walpole, could still have removed his ministers at will. Walpole was actually afraid of being removed towards the end of George I's reign, but such fears were put to an end when George I died in Osnabrück from a stroke on June 11, 1727. George I was on his sixth trip to his native Hanover, where he was buried, in Chapel Schloss Herrenhausen.