Peter Andreas Hansen (born 8 December 1795, Tønder, Schleswig, Denmark; died 28 March 1874, Gotha, Thuringia, Germany) was a Danish-born German astronomer.

He had, however, long been a student of science; and Dr Dircks, a physician practising at Tønder, prevailed with his father to send him in 1820 to Copenhagen, where he won the patronage of H.C. Schumacher and attracted the personal notice of King Frederick VI.

[2] In 1838 he published a revision of the lunar theory, entitled Fundamenta nova investigationis, &c., and the improved Tables of the Moon ("Hansen's Lunar Tables")[3] based upon it were printed in 1857, at the expense of the British government, their merit being further recognized by a grant of £1000, and by their adoption in the Nautical Almanac as from the issue for the year 1862,[4] and other Ephemerides.

A theoretical discussion of the disturbances embodied in them (long familiarly known to lunar experts as the Darlegung) appeared in the Abhandlungen of the Saxon Academy of Sciences in 1862 to 1864.

[2] At the time of publication of Hansen's Tables of the Moon in 1857, astronomers generally believed that the lunar theory was at last complete; but within about a decade, it was noticed, and shown by Simon Newcomb, that the optimism had been unfounded: deviations between computed and observed positions began to grow at a rate showing that further refinement was necessary.

He was awarded the Copley Medal by the Royal Society in 1850, and his Solar Tables, compiled with the assistance of Christian Olufsen, appeared in 1854.