Wellington has won the Ranfurly Shield for the first time since 1981.
The Lions beat Auckland 27-0 at Eden Park on Saturday evening.
The match was also round eight of the provincial championship and another bonus points win for the capital.
Radio New Zealand's sports correspondent says the holders started strongly but a turnover after 10 minutes saw Wellington away for the first of their five tries.
There were tries to Jeremy Thrush, Hosea Gear, Dan Coles, Ross Filipo and Thomas Waldrom. Piri Weepu kicked one conversion.
There would have been more tries if there had been fewer handling errors, which also cost Auckland any chance of retaining the trophy, as they made enough line breaks to be competitive.
Wellington led 10-0 at half-time and coach Jamie Joseph says they stuck to their plan to keep attacking, knowing their history of starting well only to ease off and lose.
Wellington's eighth bonus point win in a row wasn't always pretty - there were too many mistakes for that.
But Wellington's noisy fans were not complaining while Auckland's fans can count themselves lucky the margin was not wider.
Wellington's first challenge is from Tasman next Saturday.
Northland win
Northland defeated North Harbour 35-24 on Sunday in the provincial rugby championship, giving them their second win in the series and moving them up two places to 11th.
It could be their third-last game at top level unless their relegation challenge succeeds.
Harbour needed a win to retain a chance of making the playoffs.
Wellington remain unbeaten on 40 points, with Canterbury second on 33 and Hawke's Bay third on 29 points.
