Portable sawmills are sawmills small enough to be moved easily and set up in the field. They have existed for over 100 years but grew in popularity in the United States starting in the 1970s, when the 1973 oil crisis and the back-to-the-land movement had led to renewed interest in small woodlots and in self-sufficiency. Their popularity has grown exponentially since 1982, when the portable bandsaw mill was first commercialized.

Arguably, as once used in early Canadian forest logging, the donkey engine was one of the earliest portable sawmills. It was used to winch and haul log booms across lakes and water, then winch itself across land or water to its next site, and finally it would be reconfigured to run a saw to mill the timber.

The first dedicated portable sawmills were typified by the "One Man Farmer's Sawmills" that featured large circular blades and were marketed during the early twentieth century by companies like Sears, Montgomery Ward and JC Penney. These mail-order examples were "private label" machines manufactured by the Belsaw Company. Another company that built such mills was the American Sawmill Machinery Company. Many early sawmills were designed to be belt-driven from a steam traction engine (which could also be used to transport the saw).

Prior to the advent of the portable mill, small-scale sawmills were generally cobbled-together affairs constructed and operated by (almost always) two men with a penchant for tinkering. This was, and remains, a traditional occupation for Amish men; unlike most mechanical systems, small sawmills typically do not use electricity.

With the invention of the Wood-Mizer in 1982, portable bandsaw mills represented a dramatic shift in design. Unlike traditional mills, they used a thin-kerf blade of the type used on a band saw rather than a circular blade, which reduced weight and cost, and reduced the size and weight of the bearings and support blocks. The smaller kerf on these blades dramatically increased the yield from a given log. Use of band blades also allowed for a different design where the head, consisting of the blade and a power source, moves back and forth while the log remains stationary. This is in contrast to traditional mills where the log moves on a trolley while the blade remains fixed. Many companies now manufacture and sell personal and portable sawmills, including companies like Norwood Industries, Hud Son, TimberKing and Woodland Mills.

Larger mills have recently come on the market which are portable only in sections. These cut faster and can handle larger logs but do require additional set up.

In 1989 a new type of technology came on the market, in the form of the portable Swingblade Sawmill which was designed by Peterson Sawmills in New Zealand. This type of portable sawmill utilised a much smaller, thin-kerf, single circular sawblade that pivoted 90 degrees to cut one fully-edged board in a return pass. The log no longer required turning or mounting on a trailer, and boards were fully edged, providing a substantial advantage to truly portable sawmilling. A swingblade sawmill works with the sawing head moving over a stationary log, with fully edged boards being removed . Swingblade portable sawmill blade maintenance costs are around 1/10th that of a bandsaw portable sawmill

These types of portable sawmills have found favour in remote locations and third world countries, along with farmers, builders, and log cabin builders due to their versatility. Swingblade portable sawmills have also evolved to commercial automated versions that can remain in a fixed site where logs are brought in to the mill.