James Martineau (21 April 1805 – 11 January 1900) was a British religious philosopher influential in the history of Unitarianism.
He was the brother of the atheist social theorist, abolitionist Harriet Martineau. James Martineau's children included the Pre-Raphaelite watercolourist Edith Martineau, and painter and woodcarver Gertrude Martineau.
For 45 years he was Professor of Mental and Moral Philosophy and Political Economy in Manchester New College (now Harris Manchester College, of the University of Oxford), the principal training college for British Unitarianism. He also served as its Principal and President.
Many portraits of Martineau, including one painted by George Frederick Watts, are held at London's National Portrait Gallery. In 2014, the gallery revealed that its patron, Catherine, Princess of Wales, was related to Martineau. The Princess's great-great-grandfather, Francis Martineau Lupton, was Martineau's grandnephew. The gallery also holds written correspondence between Martineau and Poet Laureate, Alfred, Lord Tennyson - who records that he "regarded Martineau as the mastermind of all the remarkable company with whom he engaged". Martineau and Lord Tennyson were familiar with Queen Victoria's son, Prince Leopold, Duke of Albany and noted that Leopold, who had often "conversed with the eminent Dr. Martineau, was considered to be a young man of a very thoughtful mind, high aims, and quite remarkable acquirements". William Ewart Gladstone said to Frances Power Cobbe "Dr Martineau is beyond question the greatest of living thinkers".
