Abstract: Arsenoflorencite-(Ce) has been found at three localities in Australia—two in South Australia, and one in Queensland. It occurs as colourless to light brown scalenohedral crystals and crystal fragments in stream sediments. Electron microprobe analysis gave Ce₂O₃ 12.97, La₂O₃ 8.62, Pr₂O₃ 3.35, Nd₂O₃ 2.40, Gd₂O₃ 1.38, Sm₂O₃ 0.38, SrO 1.99, Al₂O₃ 28.75, As₂O₅ 27.02, P₂O₅ 4.68, SO₃ 1.21%; calc, H₂O 9.36%; total 102.11%. The simplified formula is REAl₃(AsO₄)₂(OH)₆, with Ce as the dominant RE element. Arsenoflorencite-(Ce) is rhombohedral, has space group R3m with α_hex. 7.029 and c_hex. 16.517 Å, and Z = 3. Strongest X-ray powder diffraction lines are: 3.513(6)(110), 2.963(10)(113), 2.201(4)(107), 1.905(5)(303) and 1.753 Å(4)(220). Density is 4.096 (meas.) and 4.091 (calc.) g/cm³. Hardness is VHN₁₀ 170. Arsenoflorencite-(Ce) is brittle, breaks with a conchoidal fracture, and has no perceptible cleavage. The mineral is colourless in transmitted light, uniaxial positive, and has ω 1.739 and ɛ 1.745 (λ = 589 nm). Arsenoflorencite-(Ce) is the arsenate analogue of florencite-(Ce), and the name was chosen to indicate this relationship.