M3 districts are for heavy industries that generate noise, traffic or pollutants. Typical uses include power plants, solid waste transfer facilities and recycling plants, and fuel supply depots. Even in M3 districts, uses with potential nuisance effects are required to conform to minimum performance standards.

Like M2 districts, M3 districts are usually located near the waterfront and buffered from residential areas. Large M3 districts are mapped along Arthur Kill in Staten Island, along the East River shore of the South Bronx, and along Newtown Creek in Brooklyn and Queens. Smaller M3 districts, many accommodating public utilities, are located along the waterfront in all five boroughs.

The two M3 districts, both with a maximum floor area ratio of 2.0 and a maximum base height before setback of 60 feet, differ only in parking requirements. M3-1 districts are subject to the parking requirements of Section 44-21 of the Zoning Resolution and M3-2 districts, found only in Manhattan are exempt.

M3-1 zones carry a maximum FAR of 2.0 and a maximum base height before setback of 60 feet. Parking is a requirement in these districts.