|Series:||Land of the Lost|
|Relatives:||Rick Marshall |
Will Marshall 
Holly Marshall 
Jack Marshall, generally referred to as "Uncle Jack", is a fictional character featured in the original Land of the Lost television series. The character was introduced as a series regular with season three of the show, beginning with the season premiere, "After-Shock", replacing the character of Rick Marshall, played by Spencer Milligan, who had departed the series. The role of Jack Marshall was played by actor Ron Harper. As the replacement father figure on the show, he appeared in a total of thirteen episodes, including the series finale.
Jack Marshall was the brother of Rick Marshall and the uncle of Will and Holly Marshall. When the Marshall family disappeared during a routine expedition down a river, Jack Marshall set out to find them. He soon discovered what had happened to them, as he found himself engulfed by the same dimensional portal that swept the Marshalls to a veritable "Land of the Lost". His arrival coincided with the disappearance of Rick Marshall, who likewise entered a rift, never to be seen again. Jack Marshall reunited with Will and Holly and met their young Paku friend, Cha-Ka. He resided with them inside of a cave and helped them to survive in this strange and dangerous land.