Wulfstan (sometimes Wulfstan II or Lupus; died 28 May 1023) was an English Bishop of London, Bishop of Worcester, and Archbishop of York. He is thought to have begun his ecclesiastical career as a Benedictine monk. He became the Bishop of London in 996. In 1002 he was elected simultaneously to the diocese of Worcester and the archdiocese of York, holding both in plurality until 1016, when he relinquished Worcester; he remained archbishop of York until his death. It was perhaps while he was at London that he first became well known as a writer of sermons, or homilies, on the topic of Antichrist. In 1014, as archbishop, he wrote his most famous work, a homily which he titled the Sermo Lupi ad Anglos, or the Sermon of the Wolf to the English.

Besides sermons Wulfstan was also instrumental in drafting law codes for both kings Æthelred the Unready and Cnut the Great of England. He is considered one of the two major writers of the late Anglo-Saxon period in England. After his death in 1023, miracles were said to have occurred at his tomb, but attempts to have him declared a saint never bore fruit.

Wulfstan's early life is obscure, but he was certainly the uncle of one Beorhtheah, his successor at Worcester but one, and the uncle of Wulfstan of Worcester. About Wulfstan's youth we know nothing. He probably had familial ties to the Fenlands in East Anglia, and to Peterborough specifically. Although there is no direct evidence of his ever being monastic, the nature of Wulfstan's later episcopal career and his affinity with the Benedictine Reform argue that he had once studied and professed as a Benedictine monk, perhaps at Winchester. According to the Anglo-Saxon Chronicle, Wulfstan was consecrated bishop of London in 996, succeeding Aelfstan. Besides the notice in the Chronicle, the first record of his name is in a collection of nine Latin penitential letters collected by him, three of which were issued by him as bishop of London, and one by him as "Archbishop of the English". The other five letters in the collection (only one of which is addressed to Wulfstan, as archbishop) were issued by Pope Gregory V and by a Pope John (either Pope John XVII or Pope John XVIII). In the letters issued by Wulfstan as bishop of London he styles himself "Lupus episcopus", meaning "the bishop Wolf." "Lupus" is the Latin form of the first element of his Old English name, which means "wolf-stone."

In 1002 Wulfstan was elected Archbishop of York and was immediately translated to that see. Holding York also brought him control over the diocese of Worcester, as at that time it was practice in England to hold "the potentially disaffected northern archbishopric in plurality with a southern see." He held both Worcester and York until 1016, resigning Worcester to Leofsige while retaining York. There is evidence, however, that he retained influence over Worcester even after this time, and that Leofsige perhaps acted "only as a suffragan to Wulfstan." Although holding two or more episcopal sees in plurality was both uncanonical and against the spirit of the Benedictine Reform, Wulfstan had inherited this practice from previous archbishops of York, and he was not the last to hold York and Worcester in plurality.

Wulfstan must have early on garnered the favour of powerful men, particularly Æthelred king of England, for we find him personally drafting all royal law codes promulgated under Æthelred's reign from 1005 to 1016. There is no doubt that Wulfstan had a penchant for law; his knowledge of previous Anglo-Saxon law (both royal and ecclesiastical), as well as ninth-century Carolingian law, was considerable. This surely made him a suitable choice for the king's legal draftsman. But it is also likely that Wulfstan's position as archbishop of York, an important centre in the then politically sensitive northern regions of the English kingdom, made him not only a very influential man in the North, but also a powerful ally for the king and his family in the South. It is indicative of Wulfstan's continuing political importance and savvy that he also acted as legal draftsman for, and perhaps advisor to, the Danish king Cnut, who took England's West Saxon throne in 1016.

Wulfstan was one of the most distinguished and effective Old English prose writers. His writings cover a wide range of topics in an even greater range of genres, including homilies (or sermons), secular laws, religious canons, and political theory. With Ælfric of Eynsham, he is one of the two major vernacular writers in early eleventh-century England, a period which, ecclesiastically, was still very much enamoured of and greatly influenced by the Benedictine Reform. The Benedictine Reform was a movement which sought to institute monastic standards among the secular clergy, a movement made popular by the churchmen of the Carolingian Empire in the ninth and tenth centuries. The Reform promoted a regular (i.e. based on a regula, or rule) life for priests and clerics, a strict church hierarchy, the primacy of the Roman see, the authority of codified or canonical church law, and stressed the importance of catholic, that is universal, church practices throughout all Christendom. These ideas could only thrive in a social and political atmosphere which recognised the importance of both the clergy's and the laity's obedience to the authority of the church on all things spiritual, and also on many things secular and juridical. This was one of the main theoretical models behind much of Wulfstan's legal and quasi-legal writings. But Wulfstan was not blind to the fact that, in order for this Reform model to thrive in England, the English clergy and laity (especially the laity) needed to be educated in the basic tenets of the faith. Nothing less than the legitimacy of English Christendom rested on Englishmen's steadfastness on certain fundamental Christian beliefs and practices, like, for example, knowledge of Christ's life and passion, memorisation of the Pater Noster and the Apostles' Creed, proper baptism, and the correct date and method of celebrating Easter mass. It is towards the promotion of such beliefs and practices, that Wulfstan engaged in writing a number of homilies dedicated to educating both clergy and laity in those Christian fundamentals which he saw as so important for both the flourishing of Christian lives and the success of the English polity.

In a series of homilies begun during his tenure as Bishop of London, Wulfstan attained a high degree of competence in rhetorical prose, working with a distinctive rhythmical system based around alliterative pairings. He used intensifying words, distinctive vocabulary and compounds, rhetorical figures, and repeated phrases as literary devices. These devices lend Wulfstan's homilies their tempo-driven, almost feverish, quality, allowing them to build toward multiple climaxes. An example from one of his earliest sermons, titled Secundum Lucam, describes with vivid rhetorical force the unpleasantries of Hell (notice the alliteration, parallelism, and rhyme):

Wa þam þonne þe ær geearnode helle wite. Ðær is ece bryne grimme gemencged, & ðær is ece gryre; þær is granung & wanung & aa singal heof; þær is ealra yrmða gehwylc & ealra deofla geþring. Wa þam þe þær sceal wunian on wite. Betere him wære þæt he man nære æfre geworden þonne he gewurde.