Christianity had been established in the Kingdom of Wessex for only fifteen years, when King Cenwalh of Wessex invited its evangelist, St. Birinus, to build a minster church adjoining his Royal palace in Winchester. Sadly, there is no truth to the old story that the mythical King Lucius of Britain had beaten him to it in the 2nd century. If the cathedral at Dorchester-on-Thames was a wooden building, Winchester's church may have been the first stone building erected in the kingdom since the departure of the Roman administration. Perhaps, masons had arrived from Italy or Frankia to help Birinus by this time. Certainly, a 72 foot long two-celled building with square side chapels or 'portici' (the northernmost being a baptistry) was soon constructed of reused Roman stone and dedicated to SS. Peter & Paul. Traditionally, King Cenwalh immediately granted it all the land surrounding the town walls, known as the Chilcomb Estate.

Birinus' church was always later known as the 'Old Minster' and, in AD 660, ten years after his death, it became a cathedral church of its own diocese. Cenwalh had became frustrated with Birinus' Frankish successor who refused to learn Old English, so he split his bishopric in two. The regions were, in fact, reunited only three years later and the centre of the diocese returned to Dorchester. By AD 690, however, Bishop Haedda ordered the transference of his Episcopal throne to Winchester and consolidated both political and ecclesiastical control of the kingdom in this largely deserted Roman town. At the same time, Haedda translated Birinus' relics to his new cathedral, although Dorchester was to hotly dispute this in later years.

In the 8th century, probably during the episcopate of Bishop Daniel, the cathedral's rectangular chancel was rebuilt as an apse. At the same time, a small detached tower, dedicated to St. Martin, was added immediately to the west. It had an arched walkway through the centre to allow access from the cathedral directly to the Royal palace opposite. It was in the middle of the path between the two that the great St. Swithun was buried in AD 862. This successful bishop had greatly raised both the profile and prosperity of his diocese and its cathedral during a triumphant episcopate; and it may have been during his time that the building acquired the coloured window glass, painted wall decoration, beautiful carvings and multicoloured tiled floors which have been found during excavation.

Late in King Alfred's reign, steps were put in place for the founding of a new Royal church at Winchester; and this 'New Minster' was eventually erected immediately to the north of the 'Old' for his son, King Edward the Elder, in AD 901. The two were so close that "the voices of the two choirs confounded one another". The New Minster completely dominated the scene, until AD 971, when the monastic reforms of Bishop Aethelwold meant that many new buildings had to be raised for the Old Minster to fulfil its role as a model of the Benedictine Order in England. It was to serve as both monastery and cathedral church, a form known as a "cathedral priory," unknown outside of England. As well as the usual cloister, refectory and dormitories, Aethelwold provided a plumbing system and surrounded the enclave with a new boundary wall after exchanging some land with itself neighbouring rival. With so much construction work taking place, Aethelwold evidently felt it was an ideal time to raise the profile and, indeed, the complete façade of his cathedral. He translated St. Swithun's bones to a rich shrine displayed in the cathedral nave and erected a massive 100ft tower over the site of the old grave; thus joining the cathedral to the small tower of St. Martin. It had vast apsidal side chapel, forming a martyrium bigger than Charlemagne's great octagon at Aachen. King Edgar may have signed reforming Regularis Concordia here in AD 973. A year later, probably while building work was still incomplete, there was a change of plan however. St. Swithun's relics were divided among a number of locations in the building, and the chapels were demolished in favour of a great west front. It was a massive undertaking of purely European inspiration which allowed the monarch to have his own throne room in the cathedral's upper levels. From here he could both view the mass being celebrated at the high-altar and be seen by his subjects. Construction took six years and was dedicated in the presence of King Aethelred and the Archbishop of Canterbury in AD 980. It was an outstanding structure, as shown by Cantor Wulfstan's description of about 1005:

"He [Aethelwold] also repaired the courts [atria] of this ancient temple with lofty walls and new roofs, strengthening it in its southern and northern parts with solid porticus and divers arches. He also added many chapels with sacred altars which keep the entry of the threshold doubtful, so that whoever walks in these courts [atria] with unfamiliar tread cannot tell whence he comes or whither to return, since open doors are seen on every hand, nor does any certain path of a way appear. Standing he turns his wandering gaze hither and thither and is amazed at the Attic roofs of the Daedalian floor, until a better informed guide appears and leads him to the threshold of the furthest vestibule. Here wondering in himself he crosses himself and cannot know in his astonished breast from what place he is to get out."

Aethelwold died in AD 984 and was probably buried in a great monolithic coffin excavated immediately to the north of the high-altar. It seems that it was his successor, St. Alphege, who began work on the church's eastern regions. Not to be outdone, he raised the floor of the nave, rebuilt the baptistry in marble, extended the chancel into a vast apse, raised the high-altar over a newly created crypt, built both rectangular and apsidal side chapels, as well as a five storied bell tower and a pyramidal mausoleum at the end. Inside there was apparently a great organ which needed seventy men to operate it. The church, almost certainly England's largest and finest, was dedicated in AD 994.

Many of the rulers of ancient Wessex, as well as England, were buried here, and their bones now lie in Mortuary Chests in the choir of the cathedral. Cynegils (AD 643), Cenwalh (AD 674), Cynewulf (AD 786), Egbert (AD 839), Aethelwulf (AD 858 but not translated until later), Alfred (temporarily in AD 899), Edred (AD 955) and Canute (1035) were all buried there. Egbert was also crowned there in AD 828. In the late Saxon period, the joint ancestry of both the West Saxon and Viking monarchs was even celebrated in a magnificent stone frieze carved with episodes from the lives of their most notable forbears.