Abstract: Various embodiments of heat sinks for passive cooling of lamps are provided. In an embodiment, a heat sink comprises a top end and a bottom end that is opposite the top end along a body axis of the heat sink, an airflow passageway formed through the heat sink, an internal surface that defines the airflow passageway, and an external surface. The airflow passageway extends in general alignment with the body axis from substantially the top end of the heat sink to substantially the bottom end of the heat sink, and the airflow passageway comprises at least one airflow opening located substantially at the top end of the heat sink and at least one airflow opening located substantially at the bottom end of the heat sink.