Butis is a genus of sleeper gobies, part of the broader goby group traditionally placed in family Eleotridae (some classifications split it off as family Butidae). The atlas's five species span a broad Indo-Pacific range - Indonesia, India, Papua New Guinea, the Philippines, Japan, Malaysia, the Solomon Islands, and Thailand - typically inhabiting brackish estuaries, mangroves, and tidal creek systems rather than open freshwater. They are stout, thick-bodied, bottom-dwelling ambush predators with a broad, flattened head, running 3–6 in in the atlas.
Butis butis, the duckbill sleeper, is the best-known species by name, occasionally kept by brackish-water specialists who replicate mangrove or estuarine conditions with driftwood, leaf litter, and mild salinity. These are ambush predators that take live or meaty foods and can be aggressive toward smaller tankmates, making them a specialist rather than a community-tank fish. Conservation leans reassuring, with four of the five atlas species rated Least Concern.