Abstract: A tandem polyolefin depolymerization-metathesis process and system for converting polymer waste to smaller hydrocarbons, specifically liquid and gaseous products, which subsequently can be modified and used as feeds or co-feeds for making circular products such as circular ethylene and polyethylene. Specifically, the disclosed processes include a tandem depolymerization process step followed by a metathesis process to provide a effluent that can be separated, further processed with a subsequent depolymerization step, or both. The effluents can be supplied to downstream processing units such as a steam cracker or AROMAX® unit thereby providing an efficient method for converting polymer waste into useful circular products. Therefore, these processes and systems can expand the number of usable plastic waste streams and improve the economics of plastic waste recycling.