Lost Cities is a cross between a board game and a card game, designed in 1999 by game designer Reiner Knizia and published by both Kosmos and Rio Grande Games. The objective of the game is to mount profitable expeditions to one or more of the five lost cities (the Himalayas, the Brazilian Rain Forest, the Desert Sands, the Ancient Volcanos and Neptune's Realm); the game was originally intended as a 2-player game, but rule variants have been contributed by fans to allow 1 or 2 further players.

The game's board consists of simple areas where to make discards; card play rules are quite straightforward, but making the right choice in a given game situation can be quite difficult. Lost Cities is a rather fast-moving game; a player who started an expedition will gain points according to how much progress he makes on his expedition, and after three rounds, the player with the highest total score wins the game.