The city's name points toward an ancient settlement called Calamae, but scholars established in the 20th century that the actual site is that of Pharae, a city old enough to appear in Homer. The coastal plain was once believed to have been covered by the sea in antiquity, but Archaic-period remains — including a Temple of Poseidon — unearthed at the Akovitika area put that theory to rest. The medieval town was not originally a port; the local coast offered no shelter from storms, so the settlement grew inland, at the foot of the western outliers of Mount Taygetos. It prospered in the 11th and 12th centuries: the Arab geographer al-Idrisi called it a "large and populous" town, and five churches from that period still survive, among them the Holy Apostles church that would later bear witness to a revolution.

After the Fourth Crusade of 1205, Kalamata passed to Frankish feudal lords and became the personal domain of the Villehardouin dynasty, who ruled the Principality of Achaea. Prince William II of Villehardouin was born and died in Kalamata's castle. The town changed hands repeatedly over the following centuries — Byzantine, Ottoman, Venetian — with Venetian rule under Francesco Morosini in the late 17th century proving particularly significant. Morosini's 1685 victory in the Battle of Kalamata brought the town into Venice's "Kingdom of the Morea," and the city developed economically under Venetian administration. The Ottomans reoccupied Kalamata in 1715 and held it until 1821. The second-oldest Chamber of Commerce in the Mediterranean — after Marseille's — was established in Kalamata, a reminder of how commercially active the port became in the years after independence.

The liberation of 1821 was followed four years later by devastation. In 1825, Ibrahim Pasha of Egypt invaded on behalf of the Ottoman Empire and destroyed the city. Kalamata was rebuilt, grew, and by the 20th century had become one of the more important ports on the Mediterranean's eastern shores. World War II brought another battle: on 29 April 1941, German forces and the 2nd New Zealand Division fought near the port, an action for which the New Zealand soldier Jack Hinton received the Victoria Cross. Kalamata was occupied until September 1944. Then, on 13 September 1986, an earthquake measuring 6.2 on the surface wave magnitude scale struck. It was described at the time as "moderately strong," but it killed 20 people, injured 330 others, and caused heavy damage throughout the city. The 1742 Benakeion Archaeological Museum — a building of Venetian architecture in the old quarter — collapsed. Kalamata rebuilt again.

Kalamata is known worldwide for one product: the olive. The Kalamata olive — dark, almond-shaped, cured in brine or wine vinegar — takes its name from this city and the surrounding region of Messenia, where olive groves have been cultivated for millennia. The city exports raisins and olive oil alongside the olives themselves. It also produces a distinct local cheese, sfela, and the silk-weaving workshops of the Kalograion monastery make the Kalamata scarves for which the region is noted. The 2021 census recorded about 58,816 people in the city proper, with the wider municipality at 72,906. The Kalamata International Dance Festival draws performers and audiences from across Europe each summer. The Kalamata Dance Megaron hosts performances year-round. Composer Yanni — born Yiannis Chryssomallis in 1954 — grew up here.

The city's geography defines it: Kalamata lies where the Nedon River meets the Messenian Gulf, a deep inlet between the Mani and Messenia peninsulas. The hilltop castle to the north, ruined since 1685, still marks the city's skyline. The Cathedral of the Ypapanti, built between 1860 and 1873, nestles beneath the old Frankish castle hill; it was damaged in the 1986 earthquake and repaired. The marina and port serve ferry routes to Kythira and Crete in summer, and the airport — Kalamata International, LGKL — receives charter and scheduled flights from European cities. The railway, once connecting Kalamata to Patras through Pyrgos and Kyparissia, was discontinued in December 2010. A former extension to the port now operates as a Railway Park, with vintage steam engines on display.