No, Studio Ghibli was founded AFTER the release of Nausicaa. So, technically, Nausicaa is not a Ghibli film but it is usually considered one as the making of that film was one of the main the reasons they decided to found Studio Ghibli.
Castle of Cagliostro was Miyazaki's first feature as a director and it was released way before Nausicaa.
Bookmarks