The Reformed Church in Romania is a Calvinist denomination and the largest Protestant church in Romania. The majority of its followers are of Hungarian ethnicity and Hungarian is the main church language. The large majority of the Church's parishes are in Transylvania; according to the 2021 census, 495,380 people or 2.6% of the total population belong to the Reformed Church. About 95% of the members were of Hungarian ethnicity.

The Hungarian minority of Romania is the largest ethnic minority in Romania. As per the 2021 Romanian census, 1,002,151 people declared themselves Hungarian, while 1,038,806 people stated that Hungarian was their mother tongue.