立方烷（C₈H₈）为人工合成的烷烃，又称为五环辛烷，外观为有光泽的晶体。八个碳原子对称地排列在立方体的八个角上。此烷烃属于柏拉图烃的一种。立方烷于1964年由芝加哥大学的Dr. Philip Eaton与Thomas W. Cole首先合成。在他们合成出立方烷之前，人们曾一度认为其不可合成，因为碳碳键的键角均为90度，张力过大而不稳定。不过当此物质被合成出以后，人们发现它在动力学上很稳定。立方烷生成热、密度等均很大，因而备受瞩目。

立方烷的衍生物用途也较为广泛。如立方烷的八个顶点全被硝化后得到的八硝基立方烷是一种高能量密度的炸药。多异氰基立方烷亦是高能量密度材料。

Cubane (C₈H₈) is a synthetic hydrocarbon molecule that consists of eight carbon atoms arranged at the corners of a cube, with one hydrogen atom attached to each carbon atom. A solid crystalline substance, cubane is one of the Platonic hydrocarbons and a member of the prismanes. It was first synthesized in 1964 by Philip Eaton, a professor of chemistry at the University of Chicago. Before Eaton and Cole's work, researchers believed that cubic carbon-based molecules could not exist, because the unusually sharp 90-degree bonding angle of the carbon atoms was expected to be too highly strained, and hence unstable. Once formed, cubane is quite kinetically stable, due to a lack of readily available decomposition paths.