noun
Legal term for a person who files a petition or complaint, especially in administrative law contexts.
訴願人は、処分の取消しを求めて審査請求を行った。
The petitioner filed a request for review seeking revocation of the disposition.
申立人 is a broader term for an applicant or petitioner in various legal proceedings; 訴願人 is more narrowly used in administrative petition contexts.
Compound of 訴願 (そがん, 'petition' or 'appeal') and 人 (にん, 'person'). The term is used in Japanese administrative law.