Can non-Muslims visit mosques in Morocco?

As a rule, no: mosques in Morocco are closed to non-Muslim visitors, a practice dating back to the French Protectorate era in the early 20th century and generally maintained since independence. It isn't hostility, it's the norm across nearly the entire country, and it applies even to architecturally famous mosques you can otherwise admire and photograph from outside, like the Koutoubia in Marrakech.

The best-known exception is the Hassan II Mosque in Casablanca, completed in 1993 at King Hassan II's own instruction that it be open to visitors of any faith. Guided tours run in several languages at set times outside prayer hours and skip Fridays, the main day of communal prayer, entirely. For most visitors, it's the only working mosque in Morocco they'll ever actually step inside.

The other partial exception is more of a technicality: the Bou Inania Madrasa in Fez, built in the 1350s, is the only madrasa in Morocco ever granted the status of a full Friday mosque, yet it's also long been open to visitors as a historic monument, its religious-school function having faded while the building itself remains one of the city's most-visited sites.

Elsewhere, the respectful approach is simple: admire the exteriors, many are genuinely worth the detour on their own, keep your voice down near an open gate or courtyard, dress modestly if you're close by, and don't photograph anyone at prayer.