The Oedipus complex is a theory that says that little boys have strong feelings for their mothers and might even want to marry them when they grow up. This can make them feel competitive with their fathers and jealous of other boys who get attention from their mothers. It's named after a Greek myth about a man named Oedipus who accidentally killed his father and married his mother. This theory was developed by a man named Sigmund Freud who was a very famous doctor who studied how people's minds work. However, some people think that this theory is outdated and not always true.