Steinau is located at an elevation of around 175 metres (574 ft) above NHN in the valley of the Kinzig river which divides the hills of the Spessart (to the south) from the Vogelsberg (to the north).

The neighbouring communities are from the north (clockwise): Freiensteinau, Neuhof, Flieden, Schlüchtern, the unincorporated area Gutsbezirk Spessart which completely surrounds the Stadtteil of Marjoß, Bad Soden-Salmünster and Birstein.

On 4 July 1290, Emperor Rudolf von Habsburg granted a charter awarding Steinau the status of town and permitting it to hold a weekly market.

[3]: 32 The Brothers (Jacob and Wilhelm) Grimm, famous for their collections of fairy tales and folklore, lived in Steinau during their childhood.

[3]: 32 Jacob and Wilhelm went to live with their aunt in Hanau to finish their education, and the rest of the family remained in Steinau until 1805 in a house, Die Alte Kellerei, that still stands today at Brückentor.