In law, an appellant is the party who, having lost their claim in a lower court decision, is appealing to a higher court to have their case reconsidered. This is usually done on the basis that the lower court judge erred in the application of law.

The appellant in the new case can be either the claimant, defendant, or respondent from the lower case, depending on who was the losing party. The winning party from the lower court, however, is now the respondent.