Yes, in most places it is legal to marry someone who is older than you. There may be some restrictions on the age difference between the two people, but in general it is not uncommon for one spouse to be older than the other. In some cultures, it is even traditional for the husband to be older than the wife. In most cases, as long as both people are over the age of consent and are able to give their consent to the marriage, it should be possible for them to marry, regardless of their ages.