Teppōyama Kofun, Keyhole-shaped burial mound in Gyoda, Japan.

Teppōyama Kofun is a keyhole-shaped mound in the Sakitama Kofun Cluster, measuring 107.6 m long, with a 49.7 m round rear section 8.5 m high and a 68.1 m front section 9.5 m high; with its surrounding moat it reaches about 163 m. It is the third-largest keyhole tomb in the cluster and resembles a scaled-down Futagoyama Kofun at roughly 80 percent of its size.

Built in the second half of the 6th century, the mound is the third-largest keyhole tomb in the Sakitama cluster, about 80% the size of nearby Futagoyama Kofun. Excavations in 1967, 1983, 2008 and 2010–2015 yielded cylindrical and morning-glory haniwa, hajiki and sue ware. In the Edo period the north constriction was reshaped for the Oshi domain's gunnery range, which gave the mound its name.

The name Teppōyama, "gun hill", comes from the Edo-period gunnery range of the Oshi domain, set up at the northern constriction of the mound; the earthwork was cut to make room for it. Excavations found the firing lane, postholes for targets and the Yami-zuka, a mound where a spotter stood to check hits, plus 154 gun and cannon balls of 18 types.

Teppōyama Kofun is part of the Sakitama Kofun Cluster, a nationally designated Special Historic Site; visitors view the mounds from marked paths and must not climb on the burial mound. The site lies in Gyoda, Saitama Prefecture, and the surrounding cluster, including the nearby Futagoyama Kofun, can be seen on foot. The stone chamber has never been excavated and is not open to entry.

Radar surveys of the rear circular mound indicate a horizontal stone chamber opening to the south, not the east. Its interior has never been excavated, so it is unknown whether the burial was ever robbed. A stepped burial path leads to the entrance, which was sealed with thick clay, and a large Sue ware jar with a pierced base came from the forecourt.