Islip lies 5 miles NE of Oxford, on the N bank of the river Ray. According to tradition, Islip was the birthplace of King Edward the Confessor in 1004, who is reputed to have been baptised in the wooden Saxon church that pre-dated the current one, N of the present site. The church of St Nicholas was built in the late 12thc and largely rebuilt in the 14thc. It now comprises a chancel, a nave with S and N aisles, a W tower and a S porch. There was a drastic restoration by E. Bruton in 1861. The transitional-style N nave arcade survives with two squat round piers, and a single round-headed window is reset at the W end of the S aisle.

The battle of Islip bridge fought during the Civil War (1645) caused severe damages to the building. Substantial restoration work was carried out in 1680. It was almost entirely rebuilt in 1861.

Edward the Confessor is alleged to have given Islip to his new foundation, St Peter at Westminster, at its dedication in 1065. Copies are extant of two writs that notify Wulfwig, Bishop of Dorchester, Earl Gyrth and all the thegns of Oxfordshire of the king's gift of his birthplace to Westminster, but the abbey failed to get presentation before the Conquest.

Domesday Book records that Godric and Alwin had held Islip freely in the Confessor's reign, but makes no mention of Westminster's claim. In 1086 Islip was held by Adeline, wife of Robert d'Ivry and daughter of Hugh de Grantmesnil in commendatione, implying temporary tenure pending investigation of Westminster's case. There is no doubt that the manor was given by William I to Hugh, and by Hugh to Adeline as part of her marriage portion. She outlived her husband, dying in 1110 or 1111, and her daughter Adelize may have inherited Islip. How and when Islip passed to the De Courcy family is unknown, although the families were already connected by marriage. Gervase de Blois, abbot of Westminster (1137-57), granted the church at Islip to Helias, decanus, in return for half a mark of silver a year. Between 1203 and 1869 the descent of the advowson followed the descent of the manor (VCH).

St Nicholas now belongs to the Ray Valley benefice, comprising Ambrosden, Charlton-on-Otmoor, Islip, Merton, Noke, Oddington, Piddington and Woodeaton.

It is not known whether the N arcade was restored to its original design or affected by Bruton's gothicising influence in the 19thc. Responds and piers with engaged corner shafts are rare in Oxfordshire (Sherwood and Pevsner).

On the S side of pier 1, just above the impost, and occupying a spandrel, is a projecting grotesque carved human head, the lower half broken off. Only the top of the head and the eye sockets remain. Although it looks as if it might be Romanesque, it is probably a death mask of Richard Busby, headmaster of Westminster School, for whom the rector of Islip, Dr Robert South (1678-1716), acted as executor. Death masks were known to have been made (VCH). There is an identical one in the vestry.

The present font at Islip dates from the 15thc. An older font, supposedly that in which Edward the Confessor was baptised, used to stand in the King's Chapel, a building to the N of the church and demolished as unsafe in 1780. That font had a chequered history and now resides in the church of All Saints in Middleton Stoney, Oxfordshire (Top. Oxon.). It looks like a 14thc one, octagonal with 14thc carving, and might possibly have been recut.