Monnai (French pronunciation: [mɔnɛ] ⓘ) is a former commune in the Orne department in north-western France.

On 1 January 2016, it was merged into the new commune of La Ferté-en-Ouche.

Following the tradition, the chapel Notre-Dame-du-Vallet was built after the discovery of a statue; it was rebuilt in 16th century and again in 1862.

The old village of Ternant, mentioned for the first time in 1100, was linked to Monnai.

In 2005, the "Carrefour des Cultures" 5-day international gathering occurred in Monnai.