The Sko or Skou languages are a small language family spoken by about 7000 people, mainly along the Vanimo coast of Sandaun Province in Papua New Guinea, with a few being inland from this area and at least one just across the border in the Indonesian province of Papua (formerly known as Irian Jaya).

Skou languages are unusual among Papuan languages for being tonal; all Skou languages possess contrastive tone. Vanimo, for example, has three tones, high, mid, low.

Example minimal sets illustrating tonal contrasts in various Skou languages:

Lakes Plain languages, spoken in a discontiguous area to the southwest, are also tonal. Because of the apparent phonological similarities and sharing of stable basic words such as ‘louse’, Foley speculates the potential likelihood of a distant relationship shared between the Skou and Lakes Plain families, but no formal proposals linking the two families have been made due to insufficient evidence. Additionally according to Foley, based on some lexical and phonological similarities, the Keuw language (currently classified as a language isolate) may also possibly share a deep relationship with the Lakes Plain languages. Like the Lakes Plain languages, Keuw also possesses constrative tone.

Lepki, Kaure, and Kembra, spoken in mountainous inland regions of the Indonesia-PNG border to the southwest of the Skou-speaking area, are also tonal.

Skou languages can be isolating or polysynthetic.

Skou languages were first linked by G. Frederici in 1912. In 1941, K.H. Thomas expanded the family to its current extent.

The Sko family is not accepted by Søren Wichmann (2013), who splits it into two separate groups.