Hollandite (chemical formula: Ba(Mn4+6Mn3+2)O16) is a manganese oxide mineral.

[2] Its structure consists of double chains of MnO6 octahedra delimiting 2 × 2 tunnels.

Their nature determines the mineral species: Ba for hollandite, K for cryptomelane, Pb for coronadite, Sr for strontiomelane,[3] Tl for thalliomelane,[4] and Na for manjiroite.

[5] Pure species are rare and most 2 × 2 tectomanganates contain mixtures of several types of tunnel cations.

A mineral, with the chemical composition BaMn4+6Fe3+2O16,[6] that was first found in the Kajlidongri mine in the Jhabua district of Madhya Pradesh, India,[7] had the name hollandite until it was reclassified as ferrihollandite by the International Mineralogical Association in 2012.