Sir Theodore Martin KCB KCVO (16 September 1816 – 18 August 1909) was a Scottish poet, biographer, and translator.

Martin's translations include Dante's Vita Nuova, Oehlenschläger's Correggio and Aladdin, Heinrich Heine's Poems and Ballads, Friedrich Schiller's Wilhelm Tell, and Hertz's King René's Daughter.

He is probably best known for his Life of the Prince Consort (1874–80), the writing of which was entrusted to him by Queen Victoria, a work which won him her lifelong friendship.

He also wrote Lives of Professor Aytoun and Lord Lyndhurst.In 1851 he married Helena Faucit, a well-known actress, and author of studies on Shakespeare's Female Characters, whose Life he published in 1901.

The couple lived for some time at Bryntysilio (The Hill of St. Tyssilio) which he bought in 1861, near Llangollen, where in 1889 they were visited by the queen during her progress in Wales.