The Suffolk Regiment was an infantry regiment of the line in the British Army with a history dating back to 1685. It saw service for three centuries, participating in many wars and conflicts, including the First and Second World Wars, before being amalgamated with the Royal Norfolk Regiment to form the 1st East Anglian Regiment (Royal Norfolk and Suffolk) in 1959 which, in 1964, was further amalgamated with the 2nd East Anglian Regiment (Duchess of Gloucester's Own Royal Lincolnshire and Northamptonshire), the 3rd East Anglian Regiment (16th/44th Foot) and the Royal Leicestershire Regiment to create the present Royal Anglian Regiment.

In 1685, the Duke of Norfolk's Regiment of Foot was recruited in Norfolk and Suffolk by the Duke of Norfolk. Raised to suppress the Monmouth Rebellion, it became part of the Royal Army and its Colonel Lord Lichfield remained loyal to James II after the 1688 Glorious Revolution. He was replaced by Henry Wharton and the regiment fought throughout the 1689 to 1691 Williamite War in Ireland, including the Battle of the Boyne, the Capture of Waterford and the Siege of Limerick in 1690.

After the October 1691 Treaty of Limerick, it returned to England before being transferred to Flanders. When the Nine Years' War ended with the 1697 Treaty of Ryswick, the regiment was saved from disbandment by becoming part of the Irish establishment, then spent the War of the Spanish Succession in Jamaica. Returning to Flanders in 1742 during the War of the Austrian Succession, it fought at Dettingen in June 1743 and Fontenoy in May 1745, where it suffered 322 casualties, the largest of any British unit involved.

As a result of the 1751 army reforms, it was renamed the 12th Regiment of Foot and in 1758, the second battalion was detached to form the 65th (2nd Yorkshire, North Riding) Regiment of Foot. During the 1756 to 1763 Seven Years' War, it fought at the battles of Minden, Villinghausen and Wilhelmsthal, as well as the Siege of Cassel. In 1782, it was given a county association as the 12th (East Suffolk) Regiment of Foot.

The regiment embarked for the West Indies in 1793 and took part in the capture of Martinique, Saint Lucia and Guadeloupe in 1794. It returned to England in 1795 and then embarked for India in 1796 where it took part in operations against Tipu Sultan including the Siege of Seringapatam in April 1799 during the Fourth Anglo-Mysore War. It also took part in the Invasion of Île Bonaparte in July 1810 and the Invasion of Isle de France in November 1810 during the Napoleonic Wars.

While garrisoning the Australian Colony of Victoria in 1854, detachments from the regiment, the 40th Regiment of Foot and colonial police, suppressed the Eureka Rebellion, by gold prospectors at Ballarat. There was a skirmish involving the 12th regiment and a mob of rebellious miners. Foot police reinforcements had already reached the Ballarat government outpost on 19 October 1854. A further detachment of the 40th (2nd Somersetshire) Regiment of Foot arrived a few days behind. On 28 November, the 12th Regiment arrived to reinforce the local government camp. As they moved near where the rebels ultimately made their last stand, there was a clash, where a drummer boy, John Egan and several other members of the convoy were attacked by a mob looking to loot the wagons.

Tradition variously had it that Egan either was killed there and then or was the first casualty of the fighting on the day of the battle. However, his grave in Old Ballarat Cemetery was removed in 2001 after research carried out by Dorothy Wickham showed that Egan had survived and died in Sydney in 1860.

While still in Australia, elements of the 1st Battalion served in the New Zealand Wars between 1860 and 1867.