No, you cannot extend your Spain Visit Visa while in Spain. Extending a Spain Visit Visa is not common and is only approved in special cases, like major health problems, unavoidable events, or for humanitarian reasons. You can't extend it just for travel or ease. If you think you’ll need more than 90 days, think about applying for a long-term visa instead. To ask for an extension, you need to apply at the Foreigner’s Office in Spain before your current visa runs out and give good proof to show why you need it.