99th is the ordinal form of the number 99. 99th or Ninety-ninth may also refer to:
A fraction, , equal to one of 99 equal parts 99th Precinct, fictional police precinct in the TV series Brooklyn Nine-Nine
Geography 99th meridian east, a line of longitude 99th meridian west, a line of longitude 99th Street (disambiguation)
Military 99th Brigade (disambiguation) 99th Division (disambiguation) 99th Regiment (disambiguation) 99th Squadron (disambiguation)
Other 99th century 99th century BC
See also 99 (disambiguation) April 9, 99th day of the year in a standard year