Jacobus Theodorus known as Tabernaemontanus (né Jacob Dietrich; died August 1590) was a physician and an early botanist and herbalist, one of the "fathers of German botany" whose illustrated Neuw Kreuterbuch (Frankfurt, 1588) was the result of a lifetime's botanizing and medical practice.

It provided unacknowledged material for John Gerard's better-known Herball (London, 1597) and was reprinted in Germany throughout the 17th century.

His Latinised name is a compressed form of the Latinized name Tabernae Montanae of his home town of Bergzabern in the Palatinate.

Tabernaemontanus began as a student of two of the pioneers of Renaissance botany, first of Otto Brunfels and later of Hieronymus Bock.

In 1549 he was the private physician to Philip II, Count of Nassau-Saarbrücken and later (from 1561 on) to Marquard von Hattstein, bishop of Speyer.