Charles I’s great warship the Sovereign of the Seas is famed for its design, decoration and importance as a tool that heightened the image of English naval supremacy. By exploring its career, size, name and decoration, this article highlights the Sovereign of the Seas’ significance as a national symbol of political and cultural power. It argues that Charles’s leading warship was developed as a reaction to naval advances and current affairs in Europe. Through a diverse range of evidence including diplomatic correspondence, printed texts and artwork from both English and French institutions, as well as relating this to similar advances in the Netherlands and Sweden, the Sovereign of the Seas’ development is internationally contextualized. By comparing it with other contemporary warships, most importantly la Couronne of France, it is shown that Charles’s flagship was a product of a growing international theatre of maritime activity that was inspired by cultural and political competition, as much as it was by military escalation.