A two-stroke engine includes: an intake passage that opens out to a crank chamber; a first one-way valve provided in the intake passage and permits a flow of fluid toward the crank chamber; a scavenging port having an upstream end communicating with the crank chamber and a downstream end that opens out in a wall defining a side portion of a cylinder, wherein the downstream end communicates with a combustion chamber defined above the piston at least when the piston is at a bottom dead center, and communicates with a part of the cylinder below the piston at least when the piston is at a top dead center; and an air supply passage that communicates a part of the intake passage which is located downstream of the first one-way valve with an upstream portion of the scavenging port so as to supply air to the scavenging port during air intake.