Hovhannes Vahanian (Armenian: Հովհաննես Վահանյան), 1832 in Constantinople, Ottoman Empire - 1891 in Constantinople) was an Ottoman politician, minister, social activist, writer, and reformer of Armenian descent. He was the brother of Srpouhi Dussap.
Hovhannes Vahanian lost his father at the early age of ten. His mother, Nazli Arzumanian Vahanian, was exceptionally well educated, compared to other women in her generation. Even more unusual for her time were her activities in the public sphere. She made every possible effort to guarantee her two children, Hovhannes and Srpouhi, a higher education. She sent Hovhannes to Paris in 1848, where he studied chemistry. After his return to Istanbul in 1853, he joined the Armenian Educational Council, which had been founded the same year. There he met most of the young men who later became known as the Armenian language renewal movement as well as the main protagonists of the Armenian National Constitution.
In 1866, he became a member of the Mixed Administrative Council of the Armenian millet (Called mixed council because it was composed of Armenian clerics and laymen). His posts within the Armenian community were soon followed by positions in the Ottoman government. In 1860, he was appointed a member of the newly formed Supreme Commercial Court. In 1868, he was appointed vice-minister of Commerce; in 1869-71, he was a member of the Abkam-i Adliye (Council of Judicial Ordinances); from 1871 on, he was also an advisor in the Sultani. The same year he changed his task as an advisor in the Ministry of Education for a similar post in the Ministry of Public Works, and was the same time appointed to the Reform Commission. In 1873, he changed positions again, going once again to the Ministry of Justice. Two years later he became counselor in the same Ministry, a position he held until the end of his life. In the same year, 1875, he was appointed to the Council of State. In 1876-77, he served as Minister of Justice. In his capacity as advisor to the president of the Abkam-i Adliye, a post he also acquired in 1876, he was sent to Europe to study legal codes of procedure, which would possibly serve as a model for Ottoman use. Hovhannes Vahanian was also active in literary life, working as a writer in his free time.