Blackline

Blackline or black line may refer to:


 * Blackline (GPS company), best known for a car-tracking device that uses Global Positioning (GPS)
 * Northern line, a line on the London Underground
 * Blackline (software company), whose software offerings are Cloud-based accounting software
 * Black Lines, a 2015 album by American rock band Mayday Parade
 * Document comparison or blacklining, a computer process to identify changes in a document
 * Linea nigra (black line), pigmentation on the abdomen, most often during pregnancy
 * Black Line, a cycling team in the British National Team Sprint Championships
 * Black Line, an 1830 offensive during the Black War between British colonists and Aboriginal Australians in Tasmania