The D-class (IB1) lifeboats are inflatable boats serving in the RNLI inshore lifeboat (ILB) fleet as well as a number of Independent Lifeboats around the UK and Ireland. Although they are known as the "IB1" at times, they are the latest development of the D-class lifeboat and as such are mainly referred to as a "D-class".

Quick Facts Class overview, General characteristics ...

D-851 The Rotarian of Filey
Class overview
Name	D-class (IB1)
Builders	Inshore Lifeboat Centre, Cowes
Operators	Royal National Lifeboat Institution Some Independent lifeboats
Preceded by	D-class (EA16)
Cost	£89,000
In service	2003–
General characteristics
Class and type	Inshore Boat 1
Displacement	400 kg (880 lb)
Length	5 m (16 ft)
Beam	2 m (6.6 ft)
Draught	1.4 m (4.6 ft)
Propulsion	1 × 50 hp Mariner outboard engine
Speed	25 knots (29 mph)
Endurance	3 hours
Capacity	8
Complement	3 or 4

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This class of lifeboat is one of the smallest operated by the RNLI, and they are a common sight at lifeboat stations round the coast. Unlike other members of the ILB fleet, the D-class (IB1) does not have a rigid hull. All others with the exception of the Arancia, hovercraft and all-weather lifeboat tenders are rigid inflatable boats.

The IB1 normally has a crew of three or four and is primarily used for surfer/swimmer incidents as well as assisting in cliff incidents where the casualty is near the water. The very nature of its work requires a swift response, and the IB1 can normally be afloat very quickly.

As of February 2020 the minimum crew for an RNLI IB1 was raised from 2 to 3. Some Independent Lifeboats have different crewing levels to the RNLI.