Abstract. This research aims to explore mathematical concepts in the Cadetral Church of Christ Raja Purwokerto. This research is a descriptive-qualitative study with an ethnographic approach. Data collection is done by observation, documentation, and interviews. The data obtained in this study were then analyzed through data reduction, data presentation, and drawing conclusions. This study's results indicate mathematical concepts in the Cathedral Church of Christ the King Purwokerto. These concepts are two-dimensional plane shapes (rhombus, square, rectangle, triangle, hexagon, circle) and three-dimensional plane shapes (cube, cuboid, cylinder, octagonal prism, triangular prism, hemisphere, cuboid without lid, half-cylinder without lid), folding symmetry, similarity, congruence, geometric transformation (reflection, translation, dilation), set, and the probability that can be used as a source of contextual mathematics learning.
Keywords: Ethnomathematics, Cathedral Church of Christ the King Purwokerto, Mathematics Learning Resources