[4] Hiiumaa emerged from the Baltic Sea 8500 years ago due to isostatic uplift after the retreat of the ice cap.

[7][8] The first documented record of the island of Dageida was made by contemporary chroniclers in 1228, when Hiiumaa and the rest of Estonia were conquered by Germanic crusaders.

In 1254, Hiiumaa was divided between the Bishopric of Ösel-Wiek and the Livonian branch of the Teutonic Order, acting partly on behalf of the Hanseatic League.

Most of the island's previously numerous Swedish-speaking population emigrated or were "Estonianised" during the period of Imperial Russian rule, although a minority remained until the 20th century.

During the period of Soviet occupation (1944–1991), Hiiumaa was declared a restricted zone, closed to foreigners and to most mainland Estonians.

[4] Hiiumaa has a low relief (up to 68 m above sea level)[5] and is mostly formed of limestone, that is exposed in cliffs around parts of the island's coast.

[13] Since the end of the 1990s the island shelters a conservation project aimed at restoring populations of European mink, an endangered species of which there is about only 1,000 individual specimens left in Europe as of 2017.

[14] The bird species found on the island include black storks, golden eagles, cranes, avocets and swans.

The forests are dominated by pine and deciduous trees, the rest of the uncultivated land is covered by swamps and dunes.

[5] The exposed geology of Hiiumaa is composed of Paleozoic limestone which dips towards the South, covered by glacial sediments.

[16] In the Ordovician (c. 455 million years ago) the sea floor was hit by a meteorite forming the 4 km wide Kärdla impact structure.

The crater is well preserved at depth, with a clear rim, breccia and minerals and rocks formed from the heat and pressure of the impact.

These include terminal moraines, the two most prominent being one in the South of Island running towards the North-East and another forming the Kõpu Peninsula.

[28] In the winter, the island can be reached, conditions permitting, via a 26.5 km ice road (the longest in Europe) across the frozen Baltic Sea.