Tennyson was born in Somersby, Lincolnshire, England. He was born into a middle-class line of Tennysons, but also had a noble and royal ancestry.
His father, George Clayton Tennyson (1778–1831), was rector of Somersby (1807–1831), also rector of Benniworth (1802–1831) and Bag Enderby, and vicar of Grimsby (1815). Rev. George Clayton Tennyson raised a large family and "was a man of superior abilities and varied attainments, who tried his hand with fair success in architecture, painting, music, and poetry. He was comfortably well off for a country clergyman and his shrewd money management enabled the family to spend summers at Mablethorpe and Skegness, on the eastern coast of England". Alfred Tennyson's mother, Elizabeth Fytche (1781–1865), was the daughter of Stephen Fytche (1734–1799), vicar of St. James Church, Louth (1764) and rector of Withcall (1780), a small village between Horncastle and Louth. Tennyson's father "carefully attended to the education and training of his children".
Tennyson and two of his elder brothers were writing poetry in their teens, and a collection of poems by all three was published locally when Alfred was only 17. One of those brothers, Charles Tennyson Turner, later married Louisa Sellwood, the younger sister of Alfred's future wife; the other was Frederick Tennyson. Another of Tennyson's brothers, Edward Tennyson, was institutionalised at a private asylum.