There is no definitive answer to this question, as there is no official measurement of NFL quarterbacks' hands. However, based on available information and anecdotal evidence, it is believed that the quarterback with the smallest hands in the NFL is Russell Wilson of the Seattle Seahawks.
Wilson's hand size has been a topic of discussion since he entered the league in 2012. At his pre-draft workout, Wilson's hand size was measured at 9 inches, which is considered small for an NFL quarterback. There have been reports that Wilson's hands have grown since then, but there is no official word on how much they have increased.
Despite his small hands, Wilson has been a very successful NFL quarterback. He has led the Seahawks to six straight playoff appearances and one Super Bowl title. He has also been named to four Pro Bowl teams during his career.