VX Sagittarii (abbreviated to VX Sgr) is an extreme red supergiant or hypergiant pulsating variable star with an unusually large magnitude range located in the constellation of Sagittarius and more than one kiloparsec away from the Sun. It is one of the largest stars discovered and also one of the most luminous and massive cool supergiant stars in the Milky Way, with an average radius of 1,450 solar radii (1.01×109 km; 6.7 au) during its quiescent pulsation phase, and of 1,556 solar radii (1.083×109 km; 7.24 au) during its active pulsation phase. At those radii, an object travelling at the speed of light would take over 6 hours to go around its surface, compared to 14.5 seconds for the Sun. If this star replaced the Sun, its photosphere would extend beyond the orbit of Jupiter and near Saturn.