A visual examination of the images from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) has revealed 322 partial and closed rings that we propose represent partially or fully enclosed three-dimensional bubbles. We argue that the bubbles are primarily formed by hot young stars in massive star formation regions. We have found an average of about 1.5 bubbles per square degree. About 25% of the bubbles coincide with known radio HII regions, and about 13% enclose known star clusters. It appears that B4B9 stars (too cool to produce detectable radio HII regions) probably produce about three-quarters of the bubbles in our sample, and the remainder are produced by young OB3 stars that produce detectable radio HII regions.