According to Official Guinness Records,
The fastest baseball pitch is 105.1 mph (169.14 km/h) and was thrown by Aroldis Chapman (Cuba) for the Cincinnati Reds in a game against the San Diego Padres, at PETCO Park, San Diego, California, USA, on 24 September 2010.
For a complete list of 2010 records, please visit 2010 Guinness Records in United States.