Lignite, often referred to as brown coal, or Rosebud coal by Northern Pacific Railroad, is a soft brown fuel with characteristics that put it somewhere between coal and peat. It is considered the lowest rank of coal; it is mined in Greece, Germany, Poland, Serbia, Russia, the United States, India, Australia and many other parts of Europe and it is used almost exclusively as a fuel for steam-electric power generation. Up to 50% of Greece's electricity and 24.6% of Germany's comes from lignite power plants.

Lignite is brownish-black in color and has a carbon content of around 25-35%, a high inherent moisture content sometimes as high as 66%, and an ash content ranging from 6% to 19% compared with 6% to 12% for bituminous coal.

The energy content of lignite ranges from 10 - 20 MJ/kg (9–17 million BTU per short ton) on a moist, mineral-matter-free basis. The energy content of lignite consumed in the United States averages 15 MJ/kg (13 million BTU/ton), on the as-received basis (i.e., containing both inherent moisture and mineral matter). The energy content of lignite consumed in Victoria, Australia averages 8.4 MJ/kg (6.5 million BTU/ton). When reacted with quaternary amine, amine treated lignite (ATL) forms. ATL is used in drilling mud to reduce fluid loss.