亞爾發法縣

{{Infobox U.S. county
| state = Oklahoma
| county = Alfalfa County
| county_zh = 亞爾發法縣
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| founded =
| named for = William H. "Alfalfa Bill" Murray, ninth Governor of Oklahoma.
| seat =
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| area_total_km2 =
| area_total_sq_mi = 881
| area_land_km2 =
| area_land_sq_mi = 867
| area_water_km2 =
| area_water_sq_mi = 15
| area percentage =
| census yr = 2000
| census estimate yr =
| pop = 6105
| population_density_km2 = 3
| population_density_sq_mi = 7
| time zone = Central
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| coordinates = {{coord|{}|0|N|{}|0|W|type:adm2nd|display=title,inline}}
}}
亞爾發法縣（）是美國奧克拉荷馬州北部的一個縣，北鄰堪薩斯州。面積2,283平方公里。根據美國2000年人口普查，共有人口6,105。縣治切羅基。

成立於1907年，縣名紀念第九任州長，綽號「苜蓿比爾」的威廉·亨利·戴維斯·摩雷 (William Henry Davis "Alfalfa Bill" Murray)。