Fellin Uyezd was an administrative unit of the Livland Governorate of the Russian Empire, later of Estonia, which existed from 1745 to 1920. Its center was the town of Fellin.
The uyezd was formed in 1745 as part of the Riga Governorate. In 1796, after the transformation of the Riga Viceroyalty, Fellin Uyezd became part of the Livland Governorate. In 1920, the uyezd passed to the independent Republic of Estonia.