The star with the highest known temperature is WR 102, a Wolf-Rayet star located in the constellation Sagittarius. Its surface temperature is estimated to be around 210,000 Kelvin (378,000 degrees Fahrenheit).

It's important to note that while WR 102 currently holds the record, astronomers are constantly discovering new stars and refining their measurements. So, there's always a chance a star with an even higher temperature could be discovered in the future.