Crystal structure and crystal chemical features of a new, discovered in fumaroles of the Tolbachik volcano (Kamchatka) copper and potassium hydroxychloride - romanorlovite, with the simplified formula K ₁₁ Cu ₉ Cl ₂₅ (OH) ₄ ∙2H ₂ O (Z = 4), are reported. The mineral is tetragonal, I4/mmm, a = 17.5538(19), c = 15.8620(17) Å, V = 4887.7(9) Å ³ . The structure was determined using single-crystal XRD data and refined to R = 5.49 % for 769 unique reflections with I > 2s(I). The structure is based on two main blocks built by Cu ²⁺ -centere polyhedra. The first one includes chains consisting of edge-sharing CuCl ₄ (OH) ₂ octahedra. In the chain a fragment built by four edge-sharing Cu(1)-centered octahedral could be distinguished whereas Cu(2)-centered octahedra are connected with this fragment from both upper and lower sides. The second structural block consists of isolated Cu ₆ Cl ₁₈ clusters built by Cu(3)-centered tetragonal pyramids and Cu(4)-centered distorted tetrahedra. In a core of the cluster Cu2+ and Pb2+ cations statistically replacing each other in the same site are located. Two these basic structural blocks are connected via distorted ACl ₆ octahedra (A = Cu, K) forming pseudo-framework. K+ cations are located in the voids and channels of the pseudo-framework. Romanorlovite has the crystal-chemical formula K ₂₄ (K,Pb) ₁₆ (K,Cu,□) ₈ Cu ₂₈ (□,Cu) ₁₆ (□,Cu,Pb) ₂ Cl ₉₂ $ (Cl,9) ₈ (9,Cl) ₈ (OH) ₁₆ ∙8H ₂ O (Z = 1). Various defects revealed in its structure are discussed.