Ole Borch (Jutland, 1626 – 1690) (latinized to Olaus Borrichius) was a Danish scientist, physician, grammarian, and poet, most famous today for being the teacher at the Vor Frue Skole in Copenhagen of Nicholas Steno. Borch had studied medicine at the University of Copenhagen and distinguished himself in the plague of 1654, when a third of Copenhagen's population died. In 1655 he was patronized by Joachim Gersdorff, the royal seneschal. In 1660 he became a professor philology at the University of Copenhagen and in 1666 of chemistry and botany.
Borch was a noted traveller with his three pupils, the sons of Gersdorff, between 1660-1665 he travelled to Holland, where he visited his former pupil Steno, Johann Glauber, Giuseppe Francesco Borri and Comenius. In England he met Robert Boyle and in France he visited Melchisédech Thévenot. His well recorded journals of his travels are an important document of the European scientific climate in the 17th century.
Borch is one of the fathers of experimental science in Denmark. It was Borch who first introduced Steno to fossils such as glossopetrae which Borch used, as was common for the time, in medicines. He is the founder of Collegium Mediceum/Borchs Kollegium in central Copenhagen. He extracted oxygen out of saltpeter in 1678.