High pressure pump systems with reduced pressure ripple for use with waterjet systems and other systems are described herein. A pump system configured in accordance with a particular embodiment includes four reciprocating members operably coupled to a crankshaft at 90 degree phase angles. The reciprocating members can include plungers operably disposed in corresponding cylinders and configured to compress fluid (e.g., water) in the cylinders to pressures suitable for waterjet processing, such as pressures exceeding 30,000 psi.