Vehicle occupant restraint systems that include a compact, web-mounted airbag that can be deployed during a crash event are described herein. In some embodiments, the web (e.g., a shoulder belt) passes through the stowed airbag during normal use and, when the airbag inflates and deploys, the airbag extends along the length of the web (for example, along the entire length, or at least most of the length, of the web) to protect the occupant. In some embodiments, the restraint systems include shoulder belts having first and second overlapping web portions, and when the airbag inflates and deploys, the airbag extends along the length of the first web portion between the first web portion and the second web portion.