Hamsey is a village and civil parish in the Lewes district of East Sussex, England. The parish covers a large area (1,144 hectares (2,830 acres)) and also consists of the villages Offham and Cooksbridge. The main centres of population in the parish are now Offham and Cooksbridge. Around the main settlements are enlarged fields, isolated old cottages and farms. The winding and undulating parish lanes between banks, old hedge rows, trees, flowery verges and ditches are popular with cyclists and give good views of the Downs. In 2011 the parish had a population of 632.

Hamsey village itself is located three miles (5 km) north of Lewes on the Prime Meridian. It lies just off the A275 which runs between Lewes and Forest Row, although the road passes through Hamsey parish at Offham and Cooksbridge. The fine medieval ex-parish Church of Old St. Peter's (now a Chapel of Ease) sits on a promontory amongst the meadows of the River Ouse. On the neck of the promontory, by the Hamsey Cut (part of the old Ouse Navigation) the fine old barns of the prosperous farmstead of Hamsey Place have been converted to a number of dwellings, and a large new pond created, with Canada geese. From here there is a lane that ends with Old St. Peter's church. There is a group of fairly large houses on the edge of the floodplain to the north west, including the large country house Hamsey House.

Internal shifts in population and in the central focus of the then largest estate (Coombe Place) drove a decision (1859) to build a new replacement church in the hamlet of Offham (this one was also dedicated to St. Peter).

Pronounced "Oaf-um", this village is on the A275 just north of Lewes It has a pub, the Blacksmiths Arms and the "new" St. Peter's Church built to replace the Church of Old St. Peter in 1840s. Offham hosts two Sites of Special Scientific Interest, Clayton to Offham Escarpment and Offham Marshes.

To the west Offham has two chalk pits with a new scrub woodland surrounding them. Historically the artisanal chalk pits would have been grazed and past owners have made an effort to manage the area. The managed chalk pits were a place of rich biodiversity with many rare species and were used by local people for recreation and wild camping. More recently the chalk pits appear to have been left unmanaged and much of the grasslands have turned to scrub. Now the scrub is heavily encroaching on the Offham double-bostal on the north west side of the spur, which is extremely biodiverse. The northern chalk pit has signs threatening £20,000 fines to be issued by Natural England for wild camping on the site. They have become a running sore with local people and conservationists, although they are still very beautiful and spotted orchids and glowworms can still be found there.

Cooksbridge is centred on its railway station and has a primary school and a pub, the Rainbow. The name Cooksbridge is first recorded in 1590 and is likely to have come from a family of that name who were recorded in Hamsey in 1543. However, in folklore the village got its name from the cooks who fed the soldiers of Simon de Montfort from the bridge on their way to the Battle of Lewes in 1264. The troops came from nearby Fletching where they spent the night in prayer on their way to the defeat of Henry III.

In the 18th and 19th century, the road was under the control of the Offham to Wych Cross Turnpike Trust. With the coming of the railway to Cooksbridge in 1847 the trustees, no doubt concerned by the increase in traffic that the station might generate, agreed to establish a turnpike (toll road) at Cooksbridge at its meeting in Lewes on the 12 Oct 1847. It was erected adjacent to Friendly Hall.

Conyboro Park, Cooksbridge, is actually in the parish of Barcombe.