As the name implies, the flamethrower is capable of projecting a stream of burning fuel onto its target, inflicting horrendous injuries on anything caught in its blast. By far the most lethal weapon in the Xenonaut arsenal at close range, the flamethrower completely ignores cover and is capable of turning any enclosed space into a raging inferno. This makes it invaluable in ambushes or when clearing fortified positions, where a single flamethrower can incinerate countless foes with a single blast. It is also able to gut buildings in seconds, destroying any cover and leaving the surviving inhabitants with nowhere to hide.

Despite its terrifying effectiveness, the flamethrower remains an unpopular weapon among the troops. In addition to being both heavy and extremely thirsty, the flamethrower puts its user at increased risk of injury on the battlefield by forcing him to carry numerous pressurised tanks of explosive fuel on his back at all times. It is also an entirely indiscriminate weapon; careless use of the flamethrower can easily lead to the user accidentally dousing a civilian or even a comrade in napalm. Extreme caution should also be used when employing the flamethrower in enclosed spaces; it is not uncommon for an overzealous flamethrower operator to immolate himself with the blowback from his own weapon.