This article deals with a case concerning the history of cartography of the northwest coast of Borneo. The island Mompracem appears conspicuously marked and continuously on European maps from the 16th century to the 19th century, but in various positions. Curiously, it is no longer shown on maps from the 20th century onwards. This article attempts to understand which map material is reliable in terms of the location of the island and to identify its current name.