The village of Oláhdellő (Dileul-Vechi in Romanian) is situated in the middle of Transylvania, on the north side of the Mures River, in Mures county. It is 27 km from Marosvásárhely (Targu-Mures) and 2.5 km from the E60 international road. Its population in 1910 was 728, in 1992 was 256, however now is 215 (2011). In January 2020, there are 76 members in the Reformed congregation including children, of which 56 are paying members. Out of this 76, only 41 actually live in the village.

The Reformed Church of Oláhdellő is the smallest active congregation in the Mures Reformed Diocese.