Sigismondo Laire (Sigismund Leirer) (1552-1639), a Bavarian-born painter, a specialist in the “small manner” on copper and stone, is known to scholars because he was mentioned by Michelangelo Merisi da Caravaggio in his famous deposition (1603) at the trial brought against him by Giovanni Baglione, but his biographical profile and artistic activity are still very hazy to this day. Painter Laire’s main artistic activity took place in the city of Rome in the time span from 1578 until 1639, the year of the artist’s death, and began at the workshop of his master Francesco da Castello. This is sixty-one years of artistic activity in the Roman context, including the regency of ten popes. Through this book we therefore wish to reconstruct Laire’s artistic activity around 1600, between Munich, Rome and Spain, and to compile for the first time a catalog of his works.