The Roxbury Conglomerate, also informally known as Roxbury puddingstone, is a name for a rock formation that forms the bedrock underlying most of Roxbury, Massachusetts, now part of the city of Boston. The bedrock formation extends well beyond the limits of Roxbury, underlying part or all of Quincy, Canton, Milton, Dorchester, Dedham, Jamaica Plain, Brighton, Brookline, Newton, Needham, and Dover. It is named for exposures in Roxbury, Boston area.

The Roxbury Conglomerate comprises the lower part of the Boston Bay Group, which is a 5 km (3 mile) thick sequence of sedimentary rocks that fill the Neoproterozoic Boston Basin in eastern Massachusetts. The upper part of the Boston Bay Group consists of the Cambridge Argillite, which overlies the Roxbury Conglomerate. The Roxbury Conglomerate traditionally has been subdivided into three subdivisions; (1.) basal Brookline Member (conglomerate and sandstone), (2.) medial Dorchester Member (mostly sandstone with minor conglomerate) and (3.) upper Squantum Member (largely diamictite). However, these three subdivisions of the Roxbury Conglomerate complexly interfinger with each other and lack the simple layer-cake distribution that past studies have described.