Although the Association of Tennis Professionals does not formally recognise service speed records made in Challenger events due to the variance in radar guns, the serve of 263.4 km / h (163.7 mph) recorded by Australian Sam Groth at an ATP Challenger event in Busan, South Korea in May 2012 was measured using approved equipment, and other data gathered appeared within a normal range. However, John Isner holds the official record for the fastest serve at 253 km / h (157.2 mph).
who has the fastest serve in the atp tennis history at 163.4 mph
Sam Groth