Subterrene

300px|thumb|Trebelev subterrene (Soviet Union) A subterrene (, ) is a vehicle that travels underground (through solid rock or soil) much as a submarine travels underwater, either by mechanical drilling, or by melting its way forward. Subterrenes existed first in fiction as mechanical drillers, with real-world thermal designs and examples following in the second half of the 20th century.

Fictional subterrenes are often depicted as cylindrical in shape with conical drill heads at one or both ends, sometimes with some kind of tank-tread for propulsion, and described either as leaving an empty tunnel behind them, or as filling the space behind it with mining debris, as is the case with the Mole from the British puppet TV series Thunderbirds. The plausibility of such machines has declined with the advent of the real-world tunnel boring machines, which demonstrate the reality of the boring task. Tunnel boring machine themselves are not usually considered to be subterrenes, possibly because they lack the secondary attributes – mobility and independence – that are normally applied to vehicles.