A hand axe is a bifacial Stone tool typical of the lower (Acheulean) and middle Palaeolithic (Mousterian), and is the longest-used tool of human history.

Hand axes are found mainly in Africa, Europe and Northern Asia, while South Asia retained flake-industries such as the Hoabinhian.

New archaeological evidence from Baise, China shows that there were also hand axes in eastern Asia.

Older hand axes were produced by direct percussion with a stone hammer and can be distinguished by their thickness and a sinuous border. Later Mousterian handaxes were produced with a soft billet of antler or wood and are much thinner, more symmetrical and have a straight border.

An experienced flintknapper needs less than 15 minutes to produce a good quality hand axe. A simple hand axe can be made from a beach pebble in less than 3 minutes.

Hand axes are mainly made of flint, but rhyolites, phonolites, quartzites and other rather coarse rocks were used as well. Obsidian, natural volcanic glass, shatters easily and was rarely used.

A hand (med./lat.: manus, pl. manūs) is a prehensile, multi-fingered extremity located at the end of an arm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each "hand" and fingerprints remarkably similar to human fingerprints) are often described as having either "hands" or "paws" on their front limbs.

Hands are the main structures for physically manipulating the environment, used for both gross motor skills (such as grasping a large object) and fine motor skills (such as picking up a small pebble). The fingertips contain some of the densest areas of nerve endings on the body, are the richest source of tactile feedback, and have the greatest positioning capability of the body; thus the sense of touch is intimately associated with hands. Like other paired organs (eyes, feet, legs), each hand is dominantly controlled by the opposing brain hemisphere, so that handedness, or the preferred hand choice for single-handed activities such as writing with a pen, reflects individual brain functioning.

The axe, or ax, is an implement that has been used for millennia to shape, split and cut wood; to harvest timber; as a weapon; and as a ceremonial or heraldic symbol. The axe has many forms and specialized uses but generally consists of an axe head with a handle, or helve.

The earliest examples of axes have heads of stone with some form of wooden handle attached (hafted) in a method to suit the available materials and use. Axes made of copper, bronze, iron, steel appeared as these technologies developed.

The axe is an example of a simple machine, as it is a type of wedge, or dual inclined plane. This reduces the effort needed by the wood chopper. It splits the wood into two parts by the pressure concentration at the blade. The handle of the axe also acts as a lever allowing the user to increase the force at the cutting edge—not using the full length of the handle is known as choking the axe. For fine chopping using a side axe this sometimes is a positive effect, but for felling with a double bitted axe it reduces efficiency.