(written from a Production point of view)
Hugh Aodh O'Brien (born 13 June 1964; age 52) is a stuntman, stunt actor, stunt coordinator, and director who performed stunts in several episodes of Star Trek: Enterprise. He received no credit for his appearances.
O'Brien was born in New York City, New York and has started his stunt career as a member of the live car stunt group "The Hell Drivers". Since 1986 he performed stunts in over 400 television series and films and has also started a directing career beside his credits as stunt coordinator. He is married to Cindy and resides in Thousand Oaks, California. O'Brien is the owner and president of "Variegated Enterprises, Inc.", a company for stunt and stunt rigging equipment. Currently, O'Brien is serving as Treasurer of the Stuntmen's Association of Motion Pictures. 
O'Brien performed and coordinated in television series such as The Guiding Light, Days of Our Lives, Quantum Leap (starring Scott Bakula and Dean Stockwell), Dead at 21, JAG, The Big Easy, Profiler, Air America, Becker (starring Terry Farrell), Providence, Passions, Gilmore Girls, Boomtown, and Deadwood.
Among his stunt resume are also films such as Hiding Out (1987), Scrooged (1988, with John Glover, Michael J. Pollard, and Alfre Woodard), Cadillac Man (1990), The Ambulance (1990, with Megan Gallagher), Kickboxer 3: The Art of War (1992), Automatic (1994, with Daphne Ashbrook, John Glover, Jeff Kober, Stanley Kamel, Penny Johnson, Marjean Holden, Laura Stepp, and stunts by Chino Binamo, Doug Coleman, and Christopher Doyle), Die Hard: With a Vengeance (1995), Lord of Illusions (1995, with Scott Bakula and Famke Janssen), From Dusk Till Dawn (1996, with Fred Williamson, Marc Lawrence, and stunts by Jennifer Caputo, Randy Hall, Anita Hart, Rosine "Ace" Hatem, Dana Hee, Billy Hank Hooker, Buddy Joe Hooker, Tommy J. Huff, Jeff Imada, Manny Perry, Scott Wilder, and Spice Williams-Crosby), Last Man Standing (1996), Anaconda (1997), The Lost World: Jurassic Park (1997), Batman & Robin (1997, with John Glover, Mark Chadwick, Paul Sklar, and stunts by Ted Barba, Gregory J. Barnett, Richard L. Blackwell, Jay Caputo, Jennifer Caputo, Shawn Crowder, Alex Daniels, Dana Dru Evenson, Andy Gill, Dana Hee, Gene LeBell, John Meier, Rita Minor, Faith Minton, Peewee Piemonte, Mic Rodgers, Todd Bryant, Scott Workman, and Spice Williams-Crosby), Boogie Nights (1997), Go (1999), Magnolia (1999), Donnie Darko (2001), Ocean's Eleven (2001), Terminator 3: Rise of the Machines (2003, with Kristanna Loken), Starsky & Hutch (2004), Dodgeball: A True Underdog Story (2004, with William Shatner), Mission: Impossible III (2006), D-War (2007), and all three Pirates of the Caribbean films (2003, 2006, and 2007, with stunts by Tom Morga, Lisa Hoyle, Mark Aaron Wagner, Tony Angelotti, and Theo Kypri).