A front line (alternative forms: front-line or frontline) in military terminology is the position(s) closest to the area of conflict of an armed force's personnel and equipment, generally referring to maritime or land forces. When a front (an intentional or unintentional boundary) between opposing sides form, the front line is the area where the armies are engaged in conflict, especially the line of contact between the opposing forces. In a military conflict, then, when facing the front line, you face the enemy.

Front line refers to the forward-most forces on a battlefield.