Styris' remarkable knock, which included 38 runs off one over, helped Sussex beat Gloucestershire at Hove.
"I'm just pleased I got a few in the middle,' 37-year-old Styris said to a television interviewer afterwards. "I'm just a slogger these days, they all seem to go even when I don't want them to."
Sussex, the 2009 winners, posted a total of 230-4, the highest score from any team in the 2012 competition. In reply, Gloucestershire could reach only 191-8.
Styris hit nine sixes in his century. Gloucestershire's James Fuller conceded 38 runs from one over as he bowled two no balls, one of which was smashed for six by Styris, who also hit three fours and three other sixes in the same over.
Styris also claimed the early wicket of Gloucestershire's Benny Howell to leave the visitors on 16-1 in reply.
Australian Andrew Symonds holds the record for the fastest T20 century when reaching the total off 34 balls when playing for Kent against Middlesex in 2004.
Top five fastest tons
A Symonds 34 Kent v Middlesex Maidstone 2004
LP van der Westhuizen 35 Namibia v Kenya Windhoek 2011/12
YK Pathan 37 Jaipur v Mumbai Mumbai 2009/10
SB Styris 37 Sussex v Gloucestershire Hove 2012
Ahmed Shehzad 40 Barisal Burners v Duronto Rajshahi Dhaka 2011/12
