The move will put 30 jobs at risk and comes after Trinity Mirror warned in the summer that advertising revenues were falling faster than at any time in the past two decades.
At the time, the UK's largest regional newspaper publisher said it was looking to identify £20m of new cost savings by next year.
The group will close three weekly titles in North Wales including the paid-for Abergele Visitor, and free papers the Rhyl and Prestatyn Visitor and Your Vale. It will replace them with a free weekly title, the Denbighshire Visitor. Advertising-led title the Flintshire BuySell will also close.
In Lancashire, free weeklies the Midweek Advertiser and Huyton & Roby Star will close, while nearby paid-for weekly the Formby Times will be relaunched as a free title.
The offices serving these papers will be among the nine to close and two local editions of the free weekly Wirral News will also be closed.
Sara Wilde, Trinity Mirror North West regional managing director, said: "I believe these changes will strengthen the power of our products in their marketplaces and meet both the needs of advertisers and readers in the face of challenging market conditions."
Earlier this year, Trinity closed eight papers in Derby and Peterborough and last month it announced plans to relaunch its Birmingham Post broadsheet as a compact paper in the autumn.
The plan marked the start of a major shake-up to its regional titles of which the changes in Wales and the North West are the latest.
Trinity Mirror also said that the Post would drop its Saturday edition and would introduce a news room overhaul across the Midlands.
The controversial overhaul will see the introduction of a single integrated newsroom for Birmingham and a centralised production unit serving titles in the Midlands. The changes called for the introduction of multimedia journalists meaning those currently employed would have to reapply for their posts.
The newspaper publisher admitted that the revamped structure would mean fewer journalists and it has entered into consultation with staff. The NUJ has balloted members on strike action.
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