The 25-year-old, who only made his international debut last November against South Africa, beat off stiff competition from New Zealand-bound nominees Brian O'Driscoll and Paul O'Connell to scoop the honour, voted for by his fellow players.
At the third annual Irish Rugby Union Players Association awards ceremony, attended by upwards of 600 people, O'Connor admitted: "To win this award has added to a great season for me personally.
"For the other players to vote for me as the best player for 2005 gives me great pride and will only encourage me to go on to achieve greater things as my career develops. This is the top rugby award in Ireland and no one can take that away from me."
Galway-born O'Connor earned his sixth Test cap in Ireland's final 2005 Six Nations encounter, the 32-20 Cardiff loss to Grand Slam winners Wales in March.
A tigerish tackler, O'Connor lined out against Scotland, England, France and Wales in this season's Championship - putting in a ferocious 14 hits in the 19-13 Lansdowne Road defeat of England.
The openside follows in the footsteps of previous winners Malcolm O'Kelly (2003) and Gordon D'Arcy (2004).
Others to be rewarded on the night included retiring Connacht fly-half Eric Elwood, who was inducted into the IRUPA's Barker Hall of Fame after 17 seasons with the province.
Ulster scrum-half Kieran Campbell claimed the Try of the Year gong for his stunning individual effort against Stade Francais last December. The 25-year-old put Mark McCall's side on the way to a much-needed 18-10 victory over the eventual Heineken Cup finalists, taking a quick tap penalty in his own half before evading several French tacklers to score.
Departing Leinster duo Shane Jennings, who is due to leave for Leicester this summer, and David Holwell, who is returning home to Northland in New Zealand after a highly effective season with the province, were also honoured.
Holwell - who has amassed a personal tally of 271 points since coming to Dublin last October - was proclaimed as the Newcomer of the Year.
Meanwhile, baggage master supreme Paddy 'Rala' O'Reilly received a Special Merit award for his ten years of service with the Irish squad.
BT IRUPA Players' Player of the Year:Johnny O'Connor (Wasps)
IRUPA Hooke & MacDonald Unsung Hero: Shane Jennings (Leinster)
IRUPA Barker Hall of Fame:Eric Elwood (Connacht)
IRUPA Tyrone Crystal Try of the Year: Kieran Campbell (Ulster)
IRUPA Green Giant Newcomer of the Year:David Holwell (Leinster)
IRUPA Irish Life Special Merit Award: Paddy 'Rala' O'Reilly