We have designed a3He cryostat which can be inserted into a storage Dewar. This cryostat requires no external gas‐handling system and has the advantages of extremely low (and recoverable) helium consumption, fast cooldown and warm‐up times, excellent temperature range and stability, and low vibrational and electrical noise. The freedom from an external gas‐handling system allows for portability and flexibility in its uses. Design and construction of the cryostat are presented, and operation and performance are discussed in some detail. To demonstrate performance of the cryostat, we present thermal boundary resistance measurements between 0.4 and 170 K for a solid–solid interface (Rh:Fe/sapphire).