A siege machine, also known as a siege engine, is a large device designed to break or bypass heavy fortifications such as castle doors and thick city walls during siege warfare. These machines can be immobile, built on-site to attack from a distance, or mobile with wheels to approach enemy fortifications. Types of siege machines include:

• Siege towers, which allow soldiers to scale walls and attack defenders directly.
• Battering rams, used to damage walls or gates by forceful impact.
• Large ranged weapons like catapults, trebuchets, and ballistas that launch heavy projectiles to damage fortifications from afar.

Historically, siege machines were made mostly of wood, using tension, torsion, or counterweights to launch projectiles before the advent of gunpowder, which later led to artillery replacing traditional siege engines. They could range in size from small structures to large constructions equivalent to buildings

. In modern gaming contexts such as Clash of Clans, siege machines are special units that carry and deploy troops directly into enemy territory, providing strategic advantages in battle

. However, the classical definition pertains to historical mechanical devices used in warfare to breach defenses.