According to our analysis, Shoptimizer is the best among the fastest WooCommerce themes. Shoptimizer is a popular WooCommerce theme that is designed for fast loading speeds. The theme is also optimized for SEO and includes features such as lazy loading of images, optimized code, and a one-click upsell feature. The only catch is that Shoptimizer is only available as a premium theme. For a free option, you can consider eStore. It offers a basic free theme that is WooCommerce compatible and comes with basic settings to improve and customize your online store. If you want, you can always upgrade to the premium version for advanced WooCommerce features and customizability.