I wasn't sure whether you were asking which dinosaur lived the longest (as far as age) or which dinosaur survived the longest (length of time from when they first appeared to when they went extinct,) so I will give you both answers. According to the Encyclopedia Britannica, one of the longest surviving dinosaurs belonged to a group called the hypsilophodontids (pictured on this webpage type here). They lived from the late Jurassic to the late Cretaceous period.

The longest living dinosaurs were dinosaurs such as Apatosaurus, Brachiosaurus, Supersaurus, etc (these are called sauropods) and were long-necked plant eaters. They could live up to 100 years!