Whittle Rock is a granite corestone reef and navigation hazard in False Bay, Western Cape, South Africa. The reef rises from a sandy bottom at about 40 m, to a minimum depth of 3.2 m, and is a well known fishing site and recreational diving area. It has an area of about 1 km², and can affect the waves at the shore in Kalk Bay in special conditions of a long southeasterly swell. It is marked by a cardinal east buoy with sound and light signals.

Whittle Rock is about 8 km to the east of Miller's Point which is on the coast of the Cape Peninsula just south of Simon's Town, on the west side of False Bay, at 34°14.846′S 18°33.714′E / 34.247433°S 18.561900°E / -34.247433; 18.561900 The contiguous reef is a bit over 1 km east to west, and a bit under 1 km north to south. There are several outliers in the order of 100 m size range, within 100 m of the main reef, and a lot more that are smaller. Several other granite outcrops and clusters of smaller size and greater depth exist in the vicinity. The official depth of the top of the reef is 3.2 m below datum.

Minimum depth according to the chart is 3.2 m at low tide, and maximum depth at the edge of the reef is about 42 m in the south. Almost the entire reef is above 40 m, the maximum depth for most recreational diving, Most of the reef is above 30 m, the general limit for recreational diving, and a fairly large amount above 18 m, the usual limit for most entry level scuba certification to ISO 24801-2 autonomous diver.

The reef comprises a series of primary ridges with approximately northwest–southeast alignment, and secondary jointing across the main ridges, with associated relatively narrow gullies in a generally north–south direction, as can be seen from the multibeam sonar image.

Whittle Rock and the other reefs of this part of False Bay are outcrops of the Peninsula Granite, a huge batholith that was intruded into the Malmesbury Group about 630 million years ago as molten rock and crystallised deep in the earth, but has since then been exposed by prolonged erosion. The characteristic spheroidal shapes of granite boulders are a result of preferential weathering along intersecting fractures and are well displayed above sea level around Llandudno and Simonstown. Close up, the granite is a coarse-grained rock consisting of large (2–5 cm) white or pink feldspar crystals, glassy brown quartz and flakes of black mica, and occasionally containing inclusions of dark Malmesbury hornfels.

Though initially intruded at great depth, prolonged erosion eventually exposed the granite at the surface, and it and what remains of the similarly eroded Malmesbury group now form a basement upon which younger sedimentary rocks of the Table Mountain Group were deposited.

Almost all the exposed granite has been extensively weathered and is in the form of rounded corestones. The colour is generally pale to medium grey, and the surface is typically fairly rough, with clearly visible crystals, and no layered structure. The massive rock is cracked on jointing planes, in directions which tend to be characteristic of the location, and weathering and erosion has accentuated these joints, in places widening them to form deep gullies. The general direction and spacing of joints in some areas is fairly consistent over quite large areas.

There are areas of rubble, gravel, pebbles, and shell along the edges of the reef, with much of the pebbled area to the north, but the surrounding surficial unconsolidated material is predominantly fine sand at depths from 30 to 42 m. There are also scattered sand patches in locally low areas, and these often have a relatively high shell content.