| Minister From: | United States |
| Country: | Costa Rica |
| Term Start: | September 2, 1937 |
| Term End: | September 1, 1941 |
| Predecessor: | Leo R. Sack |
| Successor: | Arthur Bliss Lane |
| President: | Franklin D. Roosevelt |
| Order1: | 1st |
| Minister From1: | United States |
| Country1: | Afghanistan |
| Term Start1: | May 4, 1935 |
| Term End1: | March 16, 1936 |
| Predecessor1: | Diplomatic relations established |
| Successor1: | Louis G. Dreyfus |
| President1: | Franklin D. Roosevelt |
| Minister From2: | United States |
| Country2: | Iran |
| Term Start2: | March 19, 1934 |
| Term End2: | March 16, 1936 |
| Preceded2: | Charles C. Hart |
| Succeeded2: | Louis G. Dreyfus (1940) |
| President2: | Franklin D. Roosevelt |
| Birth Date: | 6 July 1884 |
| Birth Place: | Cherokee, Iowa |
| Death Place: | Pacific Grove, California |
| Minister From3: | United States |
| Country3: | Siam |
| Term Start3: | May 31, 1915 |
| Term End3: | October 24, 1916 |
| Predecessor3: | Fred Warner Carpenter |
| Successor3: | George Pratt Ingersoll |
| President3: | Woodrow Wilson |
| State Senate4: | Idaho |
| District4: | Twin Falls |
| Term Start4: | 1910 |
| Term End4: | 1912 |
William Harrison Hornibrook (July 6, 1884 – October 24, 1946) was an American publisher, politician, and diplomat.
Hornibrook, born on July 6, 1884, in Utah, started his career as a newspaper publisher in 1906;[1] at one point or another, he owned both the predecessors to The Columbian and the Albany Democrat-Herald, along with various other papers.[2]
In November 1906,[1] he married Yolande Wilson, with whom he had two children, a son and a daughter.[3]
A Democrat, Hornibrook was elected to the Idaho State Senate, from Twin Falls County,[4] serving from 1911 to 1912,[5] before his resignation.[6]
He served as US ambassador to Thailand (then Siam) from 1915 to 1916, later as ambassador to Iran from 1934 to 1936 and Afghanistan from 1935 to 1936, while resident in Tehran. After the recognition of the Afghan government led by King Zahir Shah in August 1934, Hornibrook was appointed the first minister to Afghanistan.[7]
From 1937–1941, he was ambassador to Costa Rica.[8] [9]
He died in March 1946, in Pacific Grove, California.[10]