Pentamethylantimony or pentamethylstiborane is an organometalllic compound containing five methyl groups bound to an antimony atom with formula Sb(CH3)5.

Pentamethylantimony can be made by reacting Sb(CH3)3Br2 with two equivalents of methyl lithium.

[2] Pentamethylantimony is more stable than pentamethylbismuth, because in lower energy trimethylbismuth, the non-bonding pair of electrons is more shielded due to the f-electrons and the lanthanoid contraction.

Although it decomposes when boiling is attempted and can explode, it has a high vapour pressure at 8 mmHg at 25 °C.

[6] Stannocene Sn(C5H5)2 combines with pentamethylantimony to produce bis(tetramethylstibonium)tetracyclopentadienylstannate ([(CH3)4Sb]2Sn(C5H5)4).

Over 250 °C this decomposes to Sb(CH3) and leaves methyl groups attached to the silica surface.