Old Faithful (Eng-gí ì-sù: "lāu sìn-si̍t") sī Bí-kok Wyoming chiu lāi chi̍t ê kan-hioh-chôaⁿ (geyser), sio̍k Yellowstone Kok-ka Kong-hn̂g ê chi̍t hūn. I sī sè-kài siāng kài tēng-sî ê tē-chit hiān-siōng chi it, bí 35 kàu 120 hun-cheng chio̍h chhèng chi̍t pái sio-chúi.

"Old Faithful" chit-ê miâ sī 19 sè-kí Washburn Thàm-chhâ (Washburn Expedition) sî só͘ hō--ê.