What is the longest distance that a golf ball has ever been hit?

8.34 kilometers ... along a paved road ...

Longest Carry of a Golf Ball, Guinness World Records. 2004. "The greatest recorded carry of a golf ball is 418.78 m (458 yards), by America's Jack Hamm, at Highlands Ranch, Colorado, USA, on July 20, 1993." 418.78 m

Long Drive Team. Cobra Golf. 2004 "Jason Zuback … Holder of the Longest Drive Ever in the Final Round of the RE/MAX World Long Drive Championship (412 Yards 2 Feet 3.5 Inches)" 377.431 m

Reed, Philip. The Man Who Cracked The Code. Los Angeles Times. 7 October 2001.
(Archived at Peace River Golf Videos 2003.) "On Sept. 25, 1974, [Mike] Austin was playing in the US National Seniors Open Championship at the Winterwood Golf Course in Las Vegas, a course since renamed Desert Rose. Austin drew back and unleashed a blast that flew more than 400 yards, bounced in front of the green and came to rest 65 yards beyond the flag-stick. That shot set the Guinness world record as the longest drive ever recorded in a PGA tournament: 515 yards." 471 m

Peterson, Ivar. Golf Clubs and Driving Distance. Ivar Peterson's Math Trek.
"In 1980, for example, the leader in driving distance on the Professional Golfers of America (PGA) Tour was Dan Pohl, who averaged 274.1 yards." 250.6 m

my name is brandon moody im 14 yrs. old i went golfing at an ohio golf club called beaver creek meadows and ihit a golf ball 308 yards. somebody comment and ask me if that is good for my age

"A Russian cosmonaut set a new record for the longest golf drive in history today after hitting a lightweight ball while tethered to the outside of the International Space Station (ISS).

The golf shot was the first of several tasks performed by Expedition 14 commander Michael Lopez-Alegria and flight engineer Mikhail Tyurin as part of a busy spacewalk that got off to a late start. Fellow crewmate, European Space Agency astronaut Thomas Reiter, provided support from inside the ISS.

Tyurin hit the 3 gram golf ball about 40 minutes into the spacewalk, using a gold-plated six-iron golf club.
NASA officials estimate the ball will travel about a million miles round the Earth before deorbiting and burning up in the planet's atmosphere in 2 to 3 days, thus posing no risk to the station or to a scheduled December shuttle mission."
Source:http://www.space.com/missionlaunches/061123_eva17.html