A Roman colonia (plural coloniae) was originally a Roman outpost established in conquered territory to secure it. Eventually, however, the term came to denote the highest status of a Roman city. It is also the origin of the modern term colony.
Under the Roman Republic, which had no standing army, bodies of their own citizens were planted in conquered towns as a kind of garrison. There were two types:
After 133 BC tribunes introduced reforms to support the urban poor to become farmers again in new colonies as agricultural settlements (e.g. Tarentum in 122 BC).
Under Caesar and Augustus thousands of Roman legionary veterans were granted lands in many coloniae in the empire and were responsible for the Romanization of many territories (mainly in the spread of Latin language and of Roman laws and customs).
According to Livy, Rome's first colonies were established in about 752 BC at Antemnae and Crustumerium, both in Latium.
Other early colonies were established at Signia in the 6th century BC, Velitrae and Norba in the 5th century BC, and Ostia, Antium, and Tarracina in the late 4th century. In this first period of colonization, which lasted down to the end of the Punic Wars, colonies were primarily military in purpose, being intended to defend Roman territory, afterwards they became large centeres for the migration of the Italic people, especially in Roman north Africa which had the largest density of Roman colonies per region basis in the Roman Empire, there, the Italic population constituted more than one third of the total population during the second century A.D and the total population of the region was fully Romanized and embraced the Roman religions (Roman Pantheon and Christianity).
Algeria for instance is the second country in the world after Italy, home to the largest number of Roman sites and remains among the most alive and well preserved.
Rome, after getting rid of its powerful rival Carthage in the year 146 BC, decided a century later to include Numidia to become the new master of North Africa. They built more than 500 cities. 
There were colonies of citizens and colonies of Latins, which differed in size, constitution, and region. Colonies of citizens were typically coastal and known as coloniae maritimae. These were small (three hundred families), close to Rome, and enjoyed no civic life of their own. Sherwin-White suggested that they were similar to the Athenian cleruchy. The Latin colonies (coloniae juris latini), on the other hand, were much larger and populated by Latins, as well as by Romans who, however, did not retain Roman citizenship. The first Latin colonies were initially founded by the Latin league.
During the Late Republic, prominent figures such as the tribune Gaius Gracchus proposed to settle Rome's landless citizens in colonies of recently conquered provinces. This concept, though popular and frequently reiterated by Roman contemporaries, failed to gain traction. Large scale settlement of landless Roman citizens in provinces would never really occur in the Roman Empire.
The first Roman colony outside Italy was probably Italica in Hispania founded in 206 BC by Publius Cornelius Scipio during the Second Carthaginian War.
New bilateral defence contracts with Falerii, Tarquinii (Etruria) Caere (again), Pomptina and Poplilia tribus (tribes) formed in territories of Antium
New Roman municipiums made from small towns around Rome: Aricia, Lanuvium, Nomentum, Pedum, Tusculum. Latin ius contracts made with Tibur, Praeneste, Lavinium, Cora (Latium) Ius comercii contracts made with Circei, Notba, Setia, Signia, Nepi, Ardea, Gabii Ius migrationi and ius connubii Ufentina tribus established (on territories of Volscus city Antium), Privernum, Velitrae, Terracia, Fondi and Fotmiae made contract with Rome (cives sine suffragio)
Colonies were not founded on a large scale until the inception of the Principate. Augustus, who needed to settle over a hundred thousand of his veterans after the end of his civil wars, began a massive colony creation program throughout his empire. However, not all colonies were new cities. Many were created from already-occupied settlements and the process of colonization just expanded them. Some of these colonies would later grow into large cities (modern day Cologne was first founded as a Roman colony). During this time, provincial cities can gain the rank of colony, gaining certain rights and privileges. After the era of the Severan emperors the new "colonies" were only cities that were granted a status (often of tax exemption), and in most cases during the Late Imperial times there was no more settlement of retired legionaries.
Roman colonies sometimes served as a potential reserve of veterans which could be called upon during times of emergency. However, these colonies more importantly served to produce future Roman citizens and therefore recruits to the Roman army.
Roman colonies played a major role in the spread of the Latin language within the central and southern Italian peninsula during the early empire. The colonies showed surrounding native populations an example of Roman life.
|Modern name||Latin name||Modern country||Roman province||Foundation or Promotion||Founder or Promotor||additional Info|
|Arles||Colonia Iulia Paterna Arelatensis Sextanorum||France||Gallia Narbonensis||45 BC||Julius Caesar|
|Belgrade||Singidunum||Serbia||Moesia Superior||239 AD||founded by Celts c.279 BC, conquered by Romans in 15 BC|
|Carteia||Carteia||Spain||Hispania Ulterior||171 BC||Roman Senate|
|Colchester||Colonia Claudia Victricensis Camulodunum||United Kingdom||Britannia / Britannia Superior / Maxima Caesariensis||49||Claudius|
|Köln||Colonia Claudia Ara Agrippinensium||Germany||Germania Inferior||50||Claudius|
|Jerusalem (on the site of)||Colonia Aelia Capitolina Hierosoloma||Israel and Palestine||Judaea||After Bar Kokhba's revolt||Hadrian|
|Lincoln||Lindum Colonia or Colonia Domitiana Lindensium||United Kingdom||Britannia / Britannia Inferior / Flavia Caesariensis||71||Domitian|
|Narbonne||Colonia Iulia Paterna Claudius Narbo Martius Decumanorum||France||Gallia / Gallia Narbonensis||118 BC||Gnaeus Domitius Ahenobarbus||refounded by Caesar in 45 BC|
|Patras||Colonia Augusta Achaica Patrensis||Greece||Achaia||After the battle of Actium||Augustus|
|Şebinkarahisar||Colonia (Κολώνεια)||Turkey||Bithynia et Pontus||1st century BC||Pompey|||
|Colonia Iulia Concordia Apamea||Turkey||Bithynia-Pontus||ca. 45 BC||Iulius Caesar|
|York||Eboracum||United Kingdom||Britannia / Britannia Inferior / Britannia Secunda||early 3rd century ||Caracalla|
|Mérida||Colonia Emerita Augusta||Spain||Hispania / Lusitania||25 BC||Augustus||for war veterans of V Alaudae and X Gemina legions|
|Sarmizegetusa||Colonia Ulpia Traiana Sarmizegetusa||Romania||Dacia||106-110||Trajan|
|Alba Iulia||Apulum||Romania||Dacia||180-192 ||Commodus|
|Cluj Napoca||Napoca||Romania||Dacia||2nd half of 2nd century||Commodus|
|Drobeta-Turnu Severin||Drobeta||Romania||Dacia||198-208 ||Septimius Severus|
|Ljubljana||Colonia Iulia Aemona||Slovenia||Illyricum||35 BC|
|Debelt||Colonia Flavia Pancensis Deultum||Bulgaria||Thracia||After the Year of the Four Emperors||Vespasian||for veterans of VIII Augusta|
|Library resources about |
Colonization in the Roman Empire