许多希腊的知识被罗马吸收，它利用敌人的不团结从意大利向外扩张，唯一真正对罗马的崛起的挑战来自 腓尼基人的殖民地迦太基, 它被击败在公元前3世纪，这一事件标志罗马统治的开始。罗马首先被国王统治，后来是元老院共和(罗马共和国), 最后在公元前1世纪成为帝国，受奥古斯都和继任的独裁者们的统治。罗马帝国势力在地中海,控制着沿岸所有国家。它的北部边界是莱茵河和多瑙河。在皇帝图拉真 （公元2世纪）统治时，帝国领土达到了最大，控制着近似5，900，000平方公里的陆地面积，包括不列颠, 罗马尼亚和部分美索不达米亚。帝国带来了和平，文明和中央政府对治下领土有效的管理，但是在3世纪一连串的内战消弱了它的经济和社会力量。在4世纪，皇帝戴克理先和君士坦丁把国家分成了东西两部分。虽然戴克里先残酷迫害基督徒，但是君士坦丁还是于313年在米兰敕令中宣布停止国家支持的对基督教的迫害，从而为帝国之后于380年将基督教作为国教埋下伏笔，使天主教会成为一个重要的组织。
Much of Greek learning was assimilated by the nascent Roman state as it expanded outward from Italy, taking advantage of its enemies' inability to unite: the only real challenge to Roman ascent came from the Phoenician colony of Carthage, and its defeat in the end of the 3rd century BCE marked the start of Roman hegemony. First governed by kings, then as a senatorial republic (the Roman Republic), Rome finally became an empire at the end of the 1st century BCE, under Augustus and his authoritarian successors. The Roman Empire had its centre in the Mediterranean Sea, controlling all the countries on its shores; the northern border was marked by the Rhine and Danube rivers. Under emperor Trajan (2nd century AD) the empire reached its maximum expansion, controlling approximately 5,900,000 km² (2,300,000 sq mi) of land surface, including Britain, Romania and parts of Mesopotamia. The empire brought peace, civilization and an efficient centralized government to the subject territories, but in the 3rd century a series of civil wars undermined its economic and social strength. In the 4th century, the emperors Diocletian and Constantine were able to slow down the process of decline by splitting the empire into a Western and an Eastern part. Whereas Diocletian severely persecuted Christianity, Constantine declared an official end to state-sponsored persecution of Christians in 313 with the Edict of Milan, thus setting the stage for the empire to later become officially Christian in about 380 (which would cause the Church to become an important institution).