John de Montmirail
French noble
Feast: 29 September (not on the universal Roman calendar; kept in the Roman Martyrology or local calendars)
Who they were
In the Cistercian monastery of Longpont in France, Blessed John de Montmirail, who from a most illustrious knight became a humble monk.
The miracles
The Roman Martyrology does not describe the miracles approved in the cause.
Why that counted as sanctity
The Roman Martyrology remembers him on 29 September as a famous knight who became a humble Cistercian monk at Longpont.
The cause
The cause continues. No postulation address is published here yet. Favours received through this person’s intercession, and offers of help, are best sent to the religious order or congregation they belonged to, or to the diocese where the cause was opened; either will pass them to the postulation.
- Roman Martyrology, 29 September (Italian Bishops' Conference, Santo del giorno)
- Wikidata Q3175596 — dates, feast day and identifiers (CC0)
- English Wikipedia — Jean de Montmirail (CC BY-SA)
Checked against the sources listed on 22 September 2026. Corrections welcome.