A synchrotilt chair includes a base, a back, a seat, and a pair of parallel links pivoted to a rear of the base and to a bottom of the back to form a four-bar linkage arrangement. A spring arrangement includes leaf springs that extend between each link and the base to bias the link and in turn the back and seat toward an upright position, with the back and seat pivoting with a synchronous motion upon recline of the back. The base, the back, the seat, and the links are shaped to receive identical chairs along a stacking direction to form a densely nested stacked arrangement for compact storage. The base has a distinctive horizontal U-shaped mid-frame structure defining a plurality of corners, and further having up legs and down legs extending upwardly and downwardly, respectively, from each of the corners, with the pair of links attached to the two rearmost ones of the up legs. The base (and also separately the back and the seat structures) are injection molded as single pieces from a reinforced polymeric material in a manner that provides a lightweight, yet surprisingly rigid and sturdy construction. Armrests are pivoted to the back and have a shape configured to allow nested stacking while also providing excellent comfort, durability, and style.