Alltyblaca is a village in the Welsh county of Ceredigion, Mid-West Wales, located on the road between Llanybydder and Llanwnnen.

This was the sister chapel to the building at Llwynrhydowen and at different times adopted the stances of the Arminian, Arian and later the Unitarian theologies.

[1] In the nineteenth century, this part of West Wales became known as the Smotyn du (Black spot) because of the predominance of Unitarianism in the area, and Alltyblacca was an important regional centre.

It is built in the same style as the Unitarian chapels at Rhydygwin, near Felinfach, and Cribyn.

Inside, there is a panelled gallery on three sides supported by iron columns manufactured at the Priory Foundry at Carmarthen.