Axonal transport, also called axoplasmic transport or axoplasmic flow, is the cellular process responsible for moving lipids, synaptic vesicles, proteins, mitochondria and other organelles to and from a neuron's cell body, through the cytoplasm of its axon called the axoplasm. Since some axons are on the order of meters long, neurons cannot rely on diffusion to carry products of the nucleus and organelles to the ends of their axons. Axonal transport is also responsible for moving molecules destined for degradation from the axon back to the cell body, where they are broken down by lysosomes.

Movement toward the cell body is called retrograde transport and movement toward the synapse is called anterograde transport.

The vast majority of axonal proteins are synthesized in the neuronal cell body and transported along axons. Some mRNA translation has been demonstrated within axons. Axonal transport occurs throughout the life of a neuron and is essential to its growth and survival. Microtubules (made of tubulin) run along the length of the axon and provide the main cytoskeletal "tracks" for transportation. Kinesin and dynein are motor proteins that move cargoes in the anterograde (forwards from the soma to the axon tip) and retrograde (backwards to the soma (cell body) directions, respectively. Motor proteins bind and transport several different cargoes including mitochondria, cytoskeletal polymers, autophagosomes, and synaptic vesicles containing neurotransmitters.

Axonal transport can be fast or slow, and anterograde (away from the cell body) or retrograde (conveys materials from axon to cell body).^{[citation needed]}

Vesicular cargoes move relatively fast (50–400 mm/day) whereas transport of soluble (cytosolic) and cytoskeletal proteins takes much longer (moving at less than 8 mm/day). The basic mechanism of fast axonal transport has been understood for decades but the mechanism of slow axonal transport is only recently becoming clear, as a result of advanced imaging techniques. Fluorescent labeling techniques such as fluorescence microscopy have enabled direct visualization of transport in neurons.

Studies have revealed that the movement of cytoskeletal "slow" cargoes is actually rapid but unlike fast cargoes, they pause frequently, making the overall transit rate much slower. The mechanism is known as the "Stop and Go" model of slow axonal transport, and has been extensively validated for the transport of the cytoskeletal protein neurofilament. The movement of soluble (cytosolic) cargoes is more complex, but appears to have a similar basis where soluble proteins organize into multiprotein complexes that are then conveyed by transient interactions with more rapidly moving cargoes moving in fast axonal transport. An analogy is the difference in transport rates between local and express subway trains. Though both types of train travel at similar velocities between stations, the local train takes much longer to reach the end of the line because it stops at every station whereas the express makes only a few stops on the way.

Anterograde (also called "orthograde") transport is movement of molecules/organelles outward, from the cell body (also called soma) to the synapse or cell membrane.

The anterograde movement of individual cargoes (in transport vesicles) of both fast and slow components along the microtubule is mediated by kinesins. Several kinesins have been implicated in slow transport, though the mechanism for generating the "pauses" in the transit of slow component cargoes is still unknown.