An astrolabe (Greek: ?st?????? astrolabon; 'star-taker') is an elaborate inclinometer; historically used by astronomers; navigators; and astrologers. Its many uses include locating and predicting the positions of the Sun; Moon; planets; and stars; determining local time given local latitude and vice-versa; surveying; triangulation; and to cast horoscopes.

It was used in classical antiquity; through the Islamic Golden Age; the European Middle Ages and Renaissance for all these purposes. In the Islamic world; it was also used to calculate the Qibla and to find the times for Salah; prayers.

There is often confusion between the astrolabe and the mariner's astrolabe. While the astrolabe could be useful for determining latitude on land; it was an awkward instrument for use on the heaving deck of a ship or in wind. The mariner's astrolabe was developed to address these issues.