刘易斯与克拉克远征(英語:Lewis and Clark expedition,1804年5月14日–1806年9月23日)是美國國內首次橫越大陸西抵太平洋沿岸的往返考察活動。領隊為美国陆军的梅里韦瑟·刘易斯上尉(Meriwether Lewis)和威廉·克拉克少尉(William Clark),該活動是由傑弗遜總統所發起。
The object of your mission is to explore the Missouri River, and such principals stream of its, as, by its course and communication with the waters of the Pacific Ocean...may offer the most direct and practicable water communication across this continent for the purpose of commerce.