A website's sitemap plays a vital role in SEO by organizing and listing the pages on a site to enhance crawlability for search engines. It serves as a roadmap, helping search engine bots understand the structure and hierarchy of content, which can lead to better indexing. Additionally, a well-structured sitemap can highlight important pages, ensuring that search engines prioritize critical content during crawling and ranking processes. This can improve a website's visibility and increase its chances of appearing in relevant search results, ultimately driving organic traffic to the site.