Publius Ostorius Scapula (died 52) was a Roman statesman and general. He was the son of Quintus Ostorius Scapula, a Praetorian guard prefect trusted by Caesar Augustus.

Scapula was the second governor of Roman Britain, between 47 and 52 AD, named by Emperor Claudius. It was an extremely difficult post since the conquest of Britain was recent and the native tribes were still fighting the occupation.

He replaced Aulus Plautius in AD 47 and began a campaign of securing the country by expanding Roman controlled areas north towards the River Trent. The native resistance had been stunned by the speed of Plautius' early conquest but by the late 40s was beginning to regroup and reorganise.

Hostile tribes from the north and west began a fresh wave of attacks in winter 47, possibly thinking that the new governor would be unwilling to fight at the end of the campaign season. Ostorius however did not hesitate in moving to crush the incursions, supposedly vowing to 'tame everything this side of the Trent and the Severn' (this taken from a later emendation to Tacitus' records). The geographical area described has led to discussion about the role of the Fosse Way as a desired frontier line during the period as it links the Trent and the Severn.

Ostorius' undertaking to tame the tribes also involved disarming the previously peaceful tribes of the south who posed no threat but would have been affronted by having their weapons confiscated. This action may have led to the first rebellion of the Iceni who persuaded their neighbours to also rise up. Ostorius' strategic strengths enabled him to defeat the natives after a difficult battle, possibly at Stonea Camp in the fens near March in Cambridgeshire.

After putting down the rebellion he began expeditions beyond the frontier, beginning with a productive campaign against the Deceangli tribe in north Wales and the Cheshire Gap in 48. This was an astute move as it divided the tribes of North Britain from those in Wales. He was recalled east however after a new rebellion by a faction of the Brigantes. This was quickly suppressed but revealed the dangers in the Romans' client kingdom system of which the Brigantes were a part; troops from Legio XIV Gemina were stationed in the area to keep the Brigantine peace. At this time Legio II Augusta held the command in the south east, Legio IX Hispana was campaigning the north east beyond the Trent, Legio XX Valeria Victrix held Colchester and Legio XIV was based at Wroxeter..

In the meantime, Caratacus, whose tribe, the Catuvellauni, had been defeated in the first phase of the conquest, had re-emerged as a leader of the Silures of south east Wales and Gloucestershire. Their rising was controlled by a programme of legionary fortress construction, driving Caratacus north into the lands of the Ordovices. Ostorius managed to force him into an open conflict, after several years of guerilla war. They fought a battle, probably near the River Severn and possibly near Caersws where the Romans defeated the British leader in 51.

The Ordovices had fortified a ridge of steep hills above the river and the difficulty of the terrain behind them made an encircling manoeuvre by the Romans impossible. Although Ostorius was concerned at the seemingly impregnable defences, Tacitus records that the eagerness and loyalty of his troops persuaded him to attack and in the end the Britons were easily defeated. Caratacus' wife and daughter were captured and his brother surrendered while Caratacus himself fled to the territory of the Brigantes. Their queen, Cartimandua however handed him over to Ostorius soon after.

After the battle, Ostorius was honoured with triumphal insignia but the victory did not entirely quell resistance in the Welsh borders. The Silures especially continued to harrass Roman troops supposedly after Ostorius had publicly said that they posed such a danger that they should be either exterminated or transplanted. A large legionary force occupied in building forts in Siluran territory was surrounded and attacked and only rescued with difficulty and considerable loss. This violent desperation on the part of the Silures can be attributed to their reaction to what Peter Salway calls Ostorius' lack of political judgement. The Silures had been galvanised by Ostorius' ill-thought out threats to destroy them and began taking Roman prisoners as hostages and distributing them amongst their neighbouring tribes. This had the effect of binding them all together and creating a new resistance movement

Ostorius died unexpectedly in 52, supposedly 'worn out with care' as Tacitus puts it, leaving Rome with a growing problem on its British frontiers. Silurian raids continued, defeating a whole legion before Aulus Didius Gallus arrived as replacement governor. The complete pacification of the area was achieved only 25 years later by Sextus Julius Frontinus.

Ostorius initiated further Romanisation during his command in the safer southern lands, founding Britain's first colony of military veterans at Camulodunum (modern Colchester) in 49 and probably building the first settlement at Verulamium. His tactical skill rather than his political acumen was his strength however. He had received a difficult brief as the Claudian lowlands were economically unspectacular and Britain's mineral wealth lay in the barbarian lands instead. Capture of these would have to wait until later years. Ostorius removed Caratacus but did not manage to wipe out the native resistance.