An ignition coil for an internal combustion engine is provided.
The ignition coil includes: a primary coil and a secondary coil magnetically coupled to each other; a second spool which the secondary coil is wound around; and a connection terminal connected to a high voltage side of the secondary coil and supported by a terminal support portion provided at the second spool. The terminal support portion includes an insertion hole portion allowing the connection terminal to be inserted in an insertion direction as a coil radial direction. The connection terminal includes a protrusion protruding outside the connection terminal in a direction orthogonally crossing the insertion direction. The protrusion is engaged to the insertion hole portion from inward in the coil radial direction.