Users will also be able to use car stereo controls to select music on the iPod device.
That's a step up for drivers, who can now listen to the iPod via an adapter that fits into a car's cassette-tape desk.
"More than 70 percent of 2007-model U.S. automobiles will offer iPod integration," said Greg Joswiak, vice president of iPod product marketing.
GM will offer iPod connections on all 56 of its models, representing millions of cars and trucks, Apple said.
Mazda's global 2007 line-up of cars and sports utility vehicles will offer an iPod feature as well.
The agreements could open new doors for the market-dominating iPod, more than 58 million of which have been sold, and for Apple's iTunes digital download store.
Drive-time listening remains a stronghold for radio broadcasters, even though many automakers install stereos compatible with competing subscription-based satellite providers XM Satellite Radio Holdings Inc. and Sirius Satellite Radio Inc. .
But an easy iPod link could accelerate the device's use on the road, just as it has become popular for pedestrians and mass-transit commuters.
Investors in satellite radio have also been anxious about a more aggressive iPod entry into automobiles. They could yet fend off an iPod as they bulk up on big-name entertainment to feed their channels, from shock-jock Howard Stern to talk show queen Oprah Winfrey, Moffett said.
GM said it would offer the "personal audio link" at dealerships for less than $160 plus installation as early as October for some car models.
The connection links to the XM Satellite digital band on GM car stereos, though a user does not have to subscribe to satellite radio to plug in an iPod.