A frontline is a line of confrontation in an armed conflict, most often a war. On either side of the frontline stand the forces of the various combatants. In modern warfare, due to the broken nature of mechanized combat, frontlines rarely form; instead a zone of confrontation comprises a wide band where forces engage in battle.

World War I featured the most clearly defined frontlines known to date: the frontline in France became marked by dug trenches almost throughout.

The term is also used to describe weapons, ships or aircraft that are of the latest fighting standard, or army units intended to serve at the frontline.

Frontline also refers to:

• Frontline (Australian TV series)
• Frontline (PBS TV series)
• Frontline Ltd (Tanker company)
• Frontline magazine