Fuel injector of an internal combustion engine and combustion engine

A fuel injector for an internal combustion engine, and configured to feed fuel to a cylinder of the internal combustion engine, comprising:

• a housing, via which the fuel injector can be mounted to the internal combustion engine;
• a valve stem;
• a valve seat;
• a valve body that engages with the valve stem and which interacts with the valve seat, and which for opening a fuel flow is moveable relative to the valve seat;
• a bellows seal, which with a first end that engages with the valve stem and a second end that engages with the housing;
• and
• a sleeve body which at least partially decouples the bellows seal from a fuel flow through the fuel injector and from fuel pressure pulsations.