The chainsaw is a melee-based weapon that has appeared in every Doom title in the series. This weapon mutilates enemies close enough to contact. At 525 hits per minute, it is roughly a quadruple-speed fist. It is often used because it conserves ammo, its "rapid fire" works well on enemies with high pain chance, which minimizes damage in melee situations, and because of its gory implications.
- Switching to the chainsaw means that there is a continuous buzzing from the chainsaw motor. When "fired", the chainsaw is shoved forward and the buzzing changes to a higher and even more intense whine. Like gunfire or a fist punch, attacking with the chainsaw will alert monsters in open areas, however merely switching to the chainsaw will not. Players who often want to provoke enemies into finding them can "fire" the chainsaw, without wasting ammo.
- The chainsaw graphics are based on scans of a real chainsaw, a McCulloch Eager Beaver (borrowed by Tom Hall from his girlfriend).
- The chainsaw "rev up" sound (DSSAWUP) is played when the player switches weapons to the chainsaw. Normally it is not played in its entirety, as the sound is cut off by the normal sound effect made by the chainsaw while selected (DSSAWIDL). It can be heard in its entirety by switching weapons to the chainsaw from any other weapon, and immediately pausing the game; and is also played completely when a new level starts with the active weapon being a chainsaw (see Intermission screen#Chainsaw sound effect). This sound effect is still used in the PlayStation and Saturn ports in its entirety but doesn't stop when the chugging/buzzing sound begins, causing the two sound effects to bleed into one another during the former's duration (this is a common effect, as sound effects in general in these ports will bleed into one another regardless of repetition).
- Doom 64's chainsaw is drastically different in terms of appearance. The saw has two blades instead of one and the letters "U.A.C." are engraved on top of the weapon. The damage inflicted by this version of the weapon is also doubled.
- Unlike other weapons which can run out of ammo, the chainsaw's fuel is unlimited and it will run forever.