The invention relates to a turbomachine combustion chamber including at least one ignition spark plug carried by an outer casing and extending in guide means carried by a wall of the chamber, the wall forming a body of revolution, the guide means comprising a tubular guide having the spark plug passing axially therethrough and mounted with axial and transverse clearance on a chimney fastened to the wall of the chamber and opening out into the chamber. In order to reduce wear of the spark plug in operation, the spark plug is mounted by being fastened in a sheath, the tubular guide being slidably mounted around the sheath.