Ada (/ˈeɪdə/ AY-də[6]) is a village in Hardin County, Ohio, United States, located about 69 miles (111 km) southwest of Toledo.

Following the 1817 Treaty of Fort Meigs, the Shawnee Indians held reservation land at Hog Creek near Ada.

Ada itself was originally called Johnstown, platted in 1853 by S. M. Johnson when the railroad was extended to that point.

The University was founded in 1871 by Henry Solomon Lehr, just eighteen years after Ada was first settled.

In 1910, President William Howard Taft visited Ada,[11] to give the fall commencement speech at Ohio Northern University.

Ada welcomed Martin Luther King Jr. to the village in January of 1968,[12] just three months before his assassination.

[13] The National Arbor Day Foundation has qualified Ada as a Tree City USA since 1981.

Hog Creek is the only waterway of note and snakes around the village to the north and the east.

[22] Retterer moved to the village in 1979 to become a mathematics professor at the local Ohio Northern University, before running for mayor for the first time in 2003.

[25] Ada Exempted Village Public School houses grades K-12 and most of the administration.

The Ada Herald is a weekly newspaper, AdaIcon.com is a news website, and WOHA, a non-commercial, religious radio station owned by Holy Family Communications.

Ada station formerly operated along the Pennsylvania Railroad and is listed on the National Register of Historic Places.