FIG. 1 is a perspective view of a side-release belt buckle showing my new design; FIG. 2 is a front view thereof; FIG. 3 is a rear view thereof; FIG. 4 is a left side view thereof; FIG. 5 is a right side view thereof; FIG. 6 is a top view thereof; FIG. 7 is a bottom view thereof; FIG. 8 is an exploded perspective view thereof; and, FIG. 9 is another exploded perspective view thereof.