An ultra-high pressure discharge lamp is provided having seal portions of a structure capable of realizing a pressure resistance of 100 atm or higher while ensuring a higher yield. The ultra-high pressure discharge lamp includes: a pair of mounts each comprising a metal foil having one end welded to an associated electrode and an opposite end welded to an associated external lead pin, and a preseal glass member embedding the metal foil therein; and a quartz envelope having an arc tube portion provided with a pair of seal portions on opposite sides thereof, the electrodes associated with the respective mounts being disposed opposite to each other in the arc tube portion, the preseal glass member being hermetically sealed in a respective one of the seal portions, wherein the preseal glass member has a portion fused to an inner peripheral surface of the respective seal portion over an entire circumference thereof.