Daniel Seiter, Saiter, or Seyter was a Viennese-born painter of the Baroque, who trained and worked in Italy.

According to Houbraken, Seiter was born on the border of Switzerland and brought up in Vienna. It is unknown who his first teacher was, but as a young man he crossed the alps to Venice, where he apprenticed with Johann Carl Loth. He copied his style so well, that even at the time Houbraken was writing (1718), it was impossible to tell whether a painting was by him or Lott. He then moved to Rome to work in the studio of Carlo Maratta, and while there, he joined the Bentvueghels and received the bent nickname of Morgenstar. His Martyrdom of St Catherine (1685) and Martyrdom of St Lawrence remained on its original place, the side walls of the vestibule of the Cybo Chapel in Santa Maria del Popolo.

Becoming successful in Rome, he married a bookseller's daughter and won a lucrative commission from Charles Emmanuel II, Duke of Savoy. The Duke's son Victor Amadeus II of Sardinia commissioned him in turn to decorate the Royal Palace of Turin in 1675, when he became duke after his father died. He liked Seiter's work so much that he knighted him. Today there is still a gallery there named after him. He also helped decorate in fresco the cupola of the chapel of the Ospedale Maggiore.

Seiter followed Victor Amadeus on his travels, and painted in Brunswick and Dresden.