Metres above the Adriatic (,, Serbo-Croatian: Metara iznad Jadrana) is the vertical datum used in Albania, Austria, Bosnia and Herzegovina, Croatia, Montenegro, North Macedonia, Serbia, and Slovenia to measure elevation, referring to the average water level of the Adriatic Sea at the Sartorio mole in the Port of Trieste.

[Map of the various vertical reference areas in Europe. {{legend|#FF9977|Countries using the Adriatic datum|undefined | upload.wikimedia.org/wikipedia/commons/5/51/Vertical///references///in///Europe.svg]

Gauge

The gauging station in the Port of Trieste was established in 1875 by the local observatory run by the military geographical institute of the Austro-Hungarian Army. The average water surface elevation at Molo Sartorio became the datum valid for the whole Austro-Hungarian monarchy. Whilst the former Yugoslavian states still use it, the Eastern Bloc successor states of Austria-Hungary like Hungary and Czechoslovakia after World War II switched to the Kronstadt Gauge of the Baltic Sea, which is 0.6747 m higher. Whilst for Austria the 1875 gauge is used as the datum, the states of former Yugoslavia use the 1900 gauge (Nadmorska visina, m/nv). In Albania (normal-orthometric height) they also refer to heights as 'metres above the Adriatic', but use a specific tide gauge in the port of Durrës.

Abbreviation

The individual countries using this datum abbreviate it in different ways depending on their local language, as follows: 'Metres above the Adriatic' may be abbreviated in English to m AA

Height differences between Austria and neighbouring countries

In Austria orthometric height is used, while its neighbours use other height systems, which leads to differences. On the state borders these differences are: (Differences: HAustria − Hneighbouring states)