A semiconductor package includes a redistribution substrate and a semiconductor chip thereon. The redistribution substrate includes a ground under-bump pattern, signal under-bump patterns laterally spaced apart from the ground under-bump pattern, first signal line patterns disposed on the signal under-bump patterns and coupled to corresponding signal under-bump patterns, and a first ground pattern coupled to the ground under-bump pattern and laterally spaced apart from the first signal line pattern. Each of the signal and ground under-bump patterns includes a first part and a second part formed on the first part and that is wider than the first part. The second part of the ground under-bump pattern is wider than the second part of the signal under-bump pattern. The ground under-bump pattern vertically overlaps the first signal line patterns. The first ground pattern does not vertically overlap the signal under-bump patterns.