Helen's Tower is a 19th-century folly on the Clandeboye Estate in Bangor, Northern Ireland. The tower was commissioned by Lord Dufferin of Clandeboye, designed by Scottish architect William Burn and completed in October 1861. The tower was named in honour of Dufferin's mother, Helen Selina Blackwood, the Lady Dufferin. The tower inspired a number of poems, which were inscribed within the building. During the First World War, soldiers of the 36th (Ulster) Division trained at Clandeboye before being sent to the front line, and the landmark tower was chosen as the model for the Ulster Tower, a monument erected at Thiepval in 1921. Helen's Tower was restored in the 1980s and is now a holiday let managed by the Landmark Trust. It is a grade A listed building, recognised as "one of the two finest memorial towers in the country".
Frederick Hamilton-Temple-Blackwood (1826–1902) inherited the title of Baron Dufferin and Claneboye, along with the Clandeboye Estate, in 1841 while still a schoolboy. On reaching the age of majority in 1847, he began a major improvement of the estate, which lies on the east coast of County Down, overlooking Belfast Lough and the town of Bangor. Like the rest of Ireland, the area was affected by the Great Famine of the 1840s, resulting in widespread poverty and destitution, and Lord Dufferin's works were done in part with the objective of providing employment to local people.
The construction of a landmark tower on the estate followed contemporary fashions in garden design, and Lord Dufferin engaged the Scottish architect William Burn, who was well established as a designer of country houses in the emerging Scottish Baronial style. This style of architecture sought to revive the spirit of 16th-century Scottish buildings, and was part of the wider Gothic revival of the 19th century. A Scottish origin also suited Lord Dufferin, who was descended from the Blackwood family of Scotland. Burn's drawings for the tower are dated 1848, and refer to the building as the gamekeeper's tower. A site on high ground in the southern part of the estate was selected, and the tower was complete by November 1850 when it was formally named Helen's Tower in honour of Lord Dufferin's mother.
Helen, Lady Dufferin, came from a literary family and was herself a noted song-writer and playwright in her time. Her sister Caroline Norton also found success as a writer, and their grandfather was Richard Brinsley Sheridan (1751–1816) playwright, poet and owner of London's Theatre Royal, Drury Lane. A number of poems were written in honour of Lady Dufferin, on the occasion of the tower's inauguration in 1850, and following her death in 1867. Several of these poems were published in the privately printed Book of Helen's Tower, and many are inscribed in the tower's interiors. Contributing poets included Robert Browning, Thomas Carlyle, Sir Edwin Arnold, Rudyard Kipling, Richard Garnett and Wilfrid Scawen Blunt. The best known of these poems is Alfred, Lord Tennyson's "Helen's Tower", published in Tiresias, and Other Poems (1885).
A close replica of Helen's Tower, the Ulster Tower, was built at Thiepval in 1921 to honour the men of the 36th (Ulster) Division who fell at the Battle of the Somme. Clandeboye Estate was used for army training by the 36th (Ulster) Division during the First World War.