Johann Nikolaus Hanff (25 September 1663 – 25 December 1711) was a North German organist and composer.
Hanff was born in Wechmar in Thuringia and worked in Eutin, Hamburg and Schleswig.
Hanff’s style, with the melody moving slowly but with rich ornamentation above a slow-moving and not very clearly individualized accompaniment, was favored by Buxtehude.
While in Hamburg, Hanff taught harpsichord and composition to the young Johann Mattheson for four years.
After the death of Bishop August Friedrich and the dissolution of the court in 1705, Hanff probably returned to Hamburg, where in 1706 and 1711 two children were born to him.