Abstract The new beudantite-group mineral oberwolfachite, ideally SrFe 3+ 3 (AsO 4 )(SO 4 )(OH) 6 , was discovered in two localities: Clara mine, Oberwolfach, Schwarzwald, Baden-Württemberg, Germany (holotype) and Monterniers mine, Lantignié, Rhône, Auvergne-Rhône-Alpes, France (cotype). The associated minerals are quartz, baryte, hematite, illite, goethite, beudantite and dussertite (Clara) and arsenogoyazite, jarosite, graulichite-(Ce), goethite and hematite (Monterniers). Oberwolfachite forms yellow to brown platy crystals up to 1 mm across or thick outer zones of mixed (oberwolfachite–beudantite) crystals up to 3 mm across. The lustre is adamantine and the streak is yellow. A distinct cleavage on {0001} is observed. Calculated density is 3.874 g⋅cm –3 . The infrared spectra are given. The chemical composition of the holotype/cotype samples are (wt.%, b.d.l. = below detection limit): K 2 O 1.25/1.86, SrO 6.41/11.15, BaO 8.13/0.45, PbO 2.18/b.d.l., Al 2 O 3 0.16/0.23, Fe 2 O 3 38.99/39.98, La 2 O 3 1.68/not determined, Ce 2 O 3 1.28/2.06, P 2 O 5 0.12/b.d.l., As 2 O 5 17.55/16.55, SO 3 12.86/14.99, H 2 O (calculated) 8.72/9.05, total 99.33/96.62. The empirical formula of the holotype sample is (Sr 0.38 Ba 0.33 K 0.16 Pb 0.06 La 0.06 Ce 0.05 ) Σ1.04 (Fe 3+ 3.03 Al 0.02 ) Σ3.05 [(SO 4 ) 1.00 (AsO 4 ) 0.95 (PO 4 ) 0.01 ](O 6.16 H 6.00 ). The crystal structures of both samples were determined using single-crystal X-ray diffraction data and refined to R = 3.13% (holotype, 293 K) and 2.65% (cotype, 170 K). Oberwolfachite is trigonal, R ${\bar 3}$ m , with a = 7.3270(3) Å, c = 17.0931(9) Å and V = 794.70(8) Å 3 (holotype), and a = 7.298(2) Å, c = 16.908(3) Å and V = 779.8(4) Å 3 (cotype); Z = 3. The strongest lines of the powder X-ray diffraction pattern of holotype [ d, Å ( I , %)( hkl )] are: 5.95 (56)(101), 3.664 (37)(110), 3.117 (16)(021), 3.082 (100)(113), 2.548 (15)(024), 2.280 (22)(107), 1.983 (26)(303) and 1.832 (19)(220).