2003 Chevy Tahoe Engine won't start

2003 Chevy Tahoe V8 Automatic 85,000 miles

My Tahoe has been driving great, no indications there was anything wrong with it. While driving down the road tonight it died and won't start. All the lights come on and everything until you turn the key and then everything dies. The engine won't even turn over. We have checked the battery. What else could it be?