2-Octyne, also known as methylpentylethyne and oct-2-yne, is a type of alkyne with a triple bond at its second carbon (the '2-' indicates the location of the triple bond in the chain). Its formula is C<sub>8</sub>H<sub>14</sub>. Its density at 25 ðC and otherwise stable conditions is 0.759 g/ml. The boiling point is 137 ðC. The average molar mass is 110.20 g/mol.
It is formed by isomerization of 1-octyne catalyzed by a Yb<sup>II</sup> complex.