- 2 Okinawa, Japan
- 1 Okinawa-jima, Japan
- 1 Oklahoma
- 1 Olcott, Frances Jenkins, 1872–1963
- 1 Old Abe
- 195 Old City
- 4 Old City Hall
- 1 Old Colony Rivet Works
- 65 Old Curiosity Shop
- 1 Old Fairmount Engine Building
- 1 Old Faithful Geyser
- 3 Old Guard State Fencibles
- 2 Old man
- 2 Old Man's Home of Philadelphia
- 1 Old Oaks Cemetery
- 3 Old Plough Tavern
- 2 Old Point Comfort, Virginia
- 1 Old style (typeface group)
- 16 Old United States Mint
- 1 Old York Road
- 1 Old York Road
- 3 Old York Road
- 11 Old York Road
- 1 Old York Road
- 1 Oldach & Co. Bookbinding
- 3 Olive branches
- 1 Oliver Farm Equipment Company
- 35 Oliver Twist
- 1 Olives
- 4 Ollier, Charles, 1788-1859
- 1 Ollier, Edmund, 1827-1886
- 2 Olliffe, Laura Cubitt
- 5 Olliffe, Sir Joseph (1808-1869)
- 28 Olney
- 1 Olney
- 7 Olney Avenue
- 1 Olney, Pennsylvania
- 4 Olympic Theatre (London, England)
- 1 Ombos, Egypt
- 1 Omnibus Co.
