Theodoros Kolokotronis (Greek: Θεόδωρος Κολοκοτρώνης) (3 April 1770 – 15 February 1843) was a Greek general and one of the leaders of the Greek War of Independence against the Ottoman Empire.

Kolokotronis' greatest success was the defeat of the Ottoman army under Mahmud Dramali Pasha at Dervenakia in 1822. In 1825, he was appointed commander-in-chief of the Greek forces in the Peloponnese. Today Kolokotronis is among the most revered of the protagonists of the War of Independence. The Kolokotroneoi were a powerful and respected clan in Arcadia in the 18th century. Their legendary pride and insubordination is commemorated in a well-known folk song from that time:

Ahorse they go to church,
Ahorse they kiss the icons,
Ahorse they receive communion
From the priest's hand.

Kolokotronis was born at Ramavouni in Messenia, and grew up in Libovitsi in Arcadia. His father, Constantine Kolokotronis, took part in an armed rebellion which was supported by Catherine the Great of Russia, but was killed in an engagement along with two of his brothers George and Harry. Theodoros joined the ranks of a Peloponnesian guerrilla band, and by age fifteen was the leader (kapetanios, which means "captain") of his own group. He had a brief stint at sea as a corsair, then in 1805 he took service on a series of ships in the Russian fleet in the Russo-Turkish War. After 1810 he served in a corps of Greek infantry in English service on Zakynthos, then a British possession, and was awarded the brevet rank of brigadier for his service against the French. From his service in the regular Russian and British forces, Kolokotronis gained valuable insights that he would later use in his career.

Kolokotronis returned to the mainland just prior to the outbreak of the war (officially, 25 March 1821) and formed a confederation of irregular Moreot klepht bands. These he tried to train and organize into something resembling a modern army. In May, he was named archistrategos or Marshal Commander-in-Chief. He was already 50 years old by this time, a fact which contributed to his sobriquet O Geros tou Morea or "The Elder of Moreas," whereby Morea was another name describing the Peloponnese. Kolokotronis' first action was the defense of Valtetsi, the village near Tripoli where his army was mustering.

He next commanded Greek troops in the siege of the coastal town of Nafplion. He took the port, and the Turkish garrison in the town's twin citadels was running low on supplies, but the disorganized Greek provisional government at Argos, just to the north, could not complete negotiations for its surrender before a large Ottoman force began marching southward to crush the rebels. Panicked, government officials abandoned Argos and began evacuations by sea at Nafplion. Only an under-strength battalion under Demetrios Ypsilantis remained to hold Larissa castle, the fortress of Argos.

Kolokotronis gathered the klephts together to march to the relief of Ypsilantis. This was quite a feat in itself, considering the near-collapse of the government and the notoriously quarrelsome nature of the klephtic bands. Even the troublesome Souliotes lent a hand. The Ottoman army from the north commanded by Mahmud Dramali Pasha, after taking Corinth, had marched to the plain of Argos. The castle of Larissa was an excellent position, commanding the whole plain. To leave such a stronghold straddling Turkish supply lines was far too dangerous. Dramali would have to reduce the fortress before moving on. Scaling the cliffs, breaching the castle's stout walls, and overcoming its resolute defenders would be no easy task. Yet, there was one weakness Dramali was unaware of: Larissa, unlike the famous Acropolis in Athens, had no spring and consequently fresh water had to be supplied from cisterns. Unfortunately for the Greeks, it was July and no rains were falling to fill the cisterns. Ypsilantis bluffed the Turks as long as he could, but towards the end of the month had to sneak his men out in the middle of the night. Dramali's men plundered the castle the next day, and he was now free to march them toward the coast to resupply. (The Greeks had pursued a scorched earth policy, and the large Ottoman force was eating through its food supplies rather quickly). Ypsilantis' defense had bought Kolokotronis and the klephts valuable time.

To his dismay, Dramali found himself cut off from his supply fleet, which had intended to land at Nafplio but was successfully blockaded by the Greek fleet under Admiral Andreas Miaoulis. Dramali reluctantly decided upon a retreat toward Corinth through the Dervenaki Pass, through which he had just come unmolested. This was exactly what Kolokotronis had been hoping for. In August 1822 his quicker-moving guerrilla forces trapped the Turks in the pass and annihilated them. A devastated Sultan Mahmud II in Constantinople was forced to turn to Muhammad Ali, ruler of the nominally Ottoman pashaluk of Egypt for help.

The Greeks resumed the siege against the fortresses at Nafplio, which fell in December. Kolokotronis is said to have ridden his horse up the steep slopes of Kastro Palamidi to celebrate his victory there; a statue in the town square commemorates the event. He is attired in something resembling the costume of a hussar topped with a plumed Corinthian helmet, which he was fond of wearing, and which foreign Philhellenes were even fonder of seeing him in. (While he seems to have enjoyed dressing like a Western European cavalryman cum Ancient Greekhoplite, he is also frequently depicted wearing the more traditional fustanella and other traditional accoutrements).

Later in the same year, Kolokotronis's political enemies in the Greek provisional government, led by Petrobey Mavromichalis, had him imprisoned in the Palamidi with Dimitris Plapoutas in the same jail, but he was released when an Egyptian army under the command of Ibrahim Pasha invaded the Morea. Ibrahim was fresh from fighting the Wahhabi rebels in Arabia, and so was used to fighting guerrillas. His troops were armed with the most modern equipment and trained by European experts. The sultan had promised his father the island of Crete as an appanage for young Ibrahim if he could crush the rebels. With his eye on the prize, he burned his way through the Peloponnese, gaining much territory but arousing much hostility in Western European public opinion, which in the long run proved disastrous for the Turks. The island of Sphacteria and Navarino had already fallen into Ibrahim's hands, and to make matters worse for Kolokotronis, he still had to be on guard against the machinations of Petrobey Mavromichalis even as he was bracing himself against the new threat. Kolokotronis used guerrilla tactics to wear Ibrahim's forces down; but given his limited resources, was unable to prevent the widespread destruction that Ibrahim left in his wake. Still, in 1825, in recognition of his military acumen and many services to the Greek cause, he was appointed commander-in-chief of Greek forces in the Peloponnese.

After the war Kolokotronis became a supporter of Count Ioannis Kapodistrias and a proponent of alliance with Russia. When the count was assassinated on 8 October 1831, Kolokotronis created his own administration in support of Prince Otto of Bavaria as a king of Greece. However, later he opposed the Bavarian dominated regency during his rule. He was charged with treason and on 7 June 1834 sentenced to death; but he was pardoned in 1835. Theodoros Kolokotronis died in 1843 in Athens one day after his son's Nicholas wedding.

In the twilight of his life, Kolokotronis had learned to write in order to complete his memoirs, which have been a perennial favorite in Greece and have been several times translated into English and other languages. Kolokotronis' famed helmet, along with the rest of his arms and armor, may today be seen in the National History Museum of Greece in Athens. In addition to the Nafplio statue mentioned earlier, there is another to be seen in Athens, in the forecourt of the Old Parliament building on Stadiou Street, near Syntagma Square.

Kolokotronis is honored by many street names. One of them in the populated cities is Kolokotroni Street in Patras. Kolokotronis is also the name of military barracks near Tripolis. Kolokotronis' portrait was depicted on the obverse of the Greek 5000 drachmas banknote of 1984 - 2001.