The ordines romani are products of a ninth-century attempt to correct liturgy across Europe. Hitherto, scholarship has almost exclusively focused on them as sources for the practices of the city of Rome, narrowly defined, disregarding how they were received creatively and reinterpreted in a set of fascinating manuscripts which do not easily fit into traditional categories. This thesis re-envisages these special texts as valuable testimonies of intent and principle. In the past few decades of scholarship, it has been made very clear that what occurred under the Carolingians in the liturgy did not involve the imposition of the Roman rite from above. What was ‘Roman’ and ‘correct’ was decided by individuals, each in their own case, and they created and edited texts for what they needed. These individuals were part of intensive networks of exchange, and, broadly, they agreed on what they were attempting to accomplish. Nevertheless, depending on their own formation, and the atmosphere of their diocese, the same ritual content could be interpreted in numerous different ways. Ultimately, this thesis aims to demonstrate the usefulness of applying new techniques of assessing liturgical manuscripts, as total witnesses whose texts interpret each other, to the ninth century. Each of the ordo romanus manuscripts of the ninth century preserves a fascinating glimpse into the process of working out what ‘correct’ liturgy looked like, by people intensely invested in that proposition. Through them, we can reconceptualise the Carolingian achievement in liturgy, more sympathetically to the great diversity on the ground, but also to the broader goals which united all of these celebrants and intellectuals. In these texts, we can see how the Carolingians really understood the Roman practices they revered, and how they brought this special holiness to their own cathedrals and monasteries through richly creative re-enactment, not thoughtless replication.