When it comes to finding the perfect 21st birthday outfit, there are many options to choose from. Depending on the style of the birthday girl, her birthday outfit can be anything from casual and cute to glam and glitzy .If the birthday girl is more on the girly side, a pretty sundress or skirt with a top that has some sparkle to it would be a great option. For something a little more casual, a cute romper or jumpsuit would be perfect. And if the birthday girl wants to go all out for her special day, a glamorous gown would be an amazing choice. No matter what style the birthday girl prefers, there are plenty of great 21st birthday outfit ideas to choose from. With so many options available, she is sure to find the perfect ensemble for her big day!