Does the iPhone 6s Plus have Optical Image Stabilization (OIS)?

Yes, the iPhone 6s Plus and 6 Plus are the only iPhone models that include optical image stabilization. However, the iPhone 6s Plus is the only model with optical image stabilization for video.
The iPhone 6s camera shares all the same features of the iPhone 6s Plus camera except OIS. Both iPhones 6s models are equipped with a rear-facing 12-megapixel iSight camera and a front-facing 5-megapixel FaceTime HD camera. You can learn more about the iPhone 6s camera here and iPhone 6s Plus camera here.