Infante is a title given to children of the reigning King of Spain. It has also historically been used by Portuguese monarchs before the country became a republic. As it is a title usually used by the children of monarchs, the style of Royal Highness is also used. The female version of the word is Infanta. Fully the style is usually:

• His Royal Highness The Infante Don [name] of Spain/Portugal, or
• Her Royal Highness The Infanta Dona [name] of Spain/Portugal.