Piano pedals are foot-operated levers at the base of a piano that change the instrument's sound in various ways. Modern pianos usually have three pedals: from left to right, the soft pedal (or una corda), the sostenuto pedal, and the sustaining pedal (or damper pedal). Some pianos omit the sostenuto pedal, or have a middle pedal with a different purpose, such as a muting function, also known as the silent piano.

The development of the piano's pedals is an evolution that began in the very earliest days of the piano and continued through the late 19th century. Throughout the years, the piano had as few as one modifying stop, and as many as six or more, before finally arriving at its current configuration of three.

The damper pedal, sustain pedal, or sustaining pedal is to the right of the other pedals, and is used more often than the other pedals. It raises all the dampers off the strings so that they keep vibrating after the player releases the key. In effect, the damper pedal makes every string on the piano a sympathetic string, creating a rich tonal quality. This effect may be behind the saying that the damper pedal is "... the soul of the piano." The damper pedal has the secondary function of allowing the player to connect into a legato texture notes that otherwise could not thus be played.

The soft pedal, or una corda pedal, was invented by Bartolomeo Cristofori. It was the first mechanism invented to modify the piano's sound. This function is typically operated by the left pedal on modern pianos. Neither of its common names—soft pedal or una corda pedal—completely describe the pedal's function. The una corda primarily modifies the timbre, not just the volume, of the piano. Soon after its invention, virtually all makers integrated the una corda as a standard fixture. On Cristofori's pianos, the una corda mechanism was operated by a hand stop, not a pedal. The stop was a knob on the side of the keyboard. When the una corda was activated, the entire action shifted to the right so that the hammers hit one string (una corda) instead of two strings (due corde). Dominic Gill says that when the hammers strike only one string, the piano "... produces a softer, more ethereal tone."

By the late 18th century, piano builders had begun triple stringing the notes on the piano. This change, affecting the una corda's function, is described by Joseph Banowetz:

On the pianos of the late eighteenth to early nineteenth centuries, the pianist could shift from the normal three-string (tre corde) position to one in which either two strings (due corde) or only one (una corda) would be struck, depending on how far the player depressed the pedal. This subtle but important choice does not exist on modern pianos, but was readily available on the earlier instruments.

The sound of the una corda on early pianos created a larger difference in color and timbre than it does on the modern piano. On the modern piano, the una corda pedal makes the hammers of the treble section hit two strings instead of three. In the case of the bass strings, the hammer normally strikes either one or two strings per note. The lowest bass notes on the piano are a single thicker string. For these notes, the action shifts the hammer so that it strikes the string on a different, lesser-used part of the hammer nose.

Edwin Good states,