This first part of the treatment of the Rubiaceae occurring in the Democratic Republic of the Congo, Rwanda and Burundi provides an introduction to the family. The classification of Robbrecht & Manen (2006) in two subfamilies and four supertribes, adapted according to a number of recent findings, is followed and outlined. This fourth largest family of Angiosperms is represented in the Flora area by about 750 species classified in some 120 genera and 27 tribes. Its position, delimitation, classification and phylogeny are briefly discussed. A survey of uses is given. Coffee is the most important commodity from this family, and the second most economic coffee species (robusta) has a central African origin. A richly illustrated survey of morphological diversity and chromosome number variation is provided. To identify material to tribal level, two tables, one for each subfamily, with distinctive characters and a synoptic key to the tribes are provided. Material can be identified to genus level using three keys, one for flowering material, one for fruiting material and a third one for complete material (flowers and fruits). The latter arranges the genera in six artificial groups. Additionally, a list of spot characters is provided to assist identification.