At the time of her design, she was not considered as being the forerunner of any class; she was designed by the Director of Naval Construction, Sir Nathaniel Barnaby, as a one-off as an answer to the French Amiral Baudin-class ironclads, which carried three heavy guns on the centreline and a number of smaller pieces on the broadside.
He made several proposals to the Board of Admiralty, but they were all rejected.
Barnaby's final submission was inspired by the four French Terrible-class ironclads laid down in 1877–78 and was a return to the configuration of Devastation with the primary armament positioned fore and aft of the central superstructure, but with the breech-loading main armament mounted in barbettes, as per the French ships, which allowed them to be sited 10 feet (3.0 m) further above the waterline than Devastation's guns.
The Board modified Barnaby's design by adding 25 feet (7.6 m) of length and  2,000 indicated horsepower (1,500 kW) to guarantee a speed of 15 knots (28 km/h; 17 mph) at deep load.
It also substituted four smaller 42-long-ton (43 t) guns for Barnaby's two 80-long-ton (81 t) guns.
The additional length and the Board's acceptance of the hull lines from Colossus increased the size of the ship by 2,500 long tons (2,540 t).

Barnaby was severely criticised, particularly by Sir Edward Reed, himself a former Chief Constructor of the Royal Navy, because Collingwood's waterline armour belt was concentrated amidships and did not extend to the ends of the ship.
Reed believed that this weakness meant that the ship could be sunk from the consequent uninhibited flooding if her unarmoured ends were riddled by shellfire and open to the sea.
Barnaby deliberately selected a hull shape with narrow, fine ends to limit the volume of the hull that could be flooded and situated the armoured deck below the waterline to prevent it from being pierced by enemy shells and flooding the lower part of the ironclad.
Furthermore, he heavily subdivided the hull to limit the amount of water that could enter through any one hit and placed coal bunkers above the armoured deck to absorb the fragments from exploding shells.
Unbeknownst to his critics, Collingwood was tested in 1884 with her ends and the large spaces in her hold ballasted with water and her draught only increased by 17.5 inches (440 mm) and she lost a minor amount of speed.
The price was that the ship lacked buoyancy at her ends and tended to bury her bow in oncoming waves rather than be lifted over them.
Her speed was greatly reduced in a head sea and the resulting spray made working the guns very difficult.
Collingwood tended to roll heavily and was not regarded as a good seaboat.
Despite these issues, her basic configuration was followed by most subsequent British ironclads and predreadnought battleships until the revolutionary Dreadnought of 1905.

The ship had a length between perpendiculars of 325 feet (99.1 m), a beam of 68 feet (20.7 m), and a draught of 27 feet 10 inches (8.5 m) at deep load.
She displaced 9,500 long tons (9,700 t) at normal load and had a complement of 498 officers and ratings.

The ship was powered by a pair of 2-cylinder inverted compound-expansion steam engines, each driving one propeller.
The Humphreys engines produced a total of 7,000 indicated horsepower (5,200 kW) at normal draught and 9,600 ihp (7,200 kW) with forced draught, using steam provided by a dozen cylindrical boilers with a working pressure of 100 psi (689 kPa; 7 kgf/cm²).
She was designed to reach a speed of 15.5 knots (28.7 km/h; 17.8 mph) at normal draught and Collingwood reached 16.6 knots (30.7 km/h; 19.1 mph) from 8,369 ihp (6,241 kW) on her sea trials, using natural draught.
She was the first British ironclad to be equipped with forced draught and the ship only reached a speed of 16.84 knots (31.19 km/h; 19.38 mph) from 9,573 ihp (7,139 kW) while using it during her sea trials because her engines were incapable of handling the additional steam.
Collingwood carried a maximum of 1,200 long tons (1,219 t) of coal that gave her a range of 8,500 nautical miles (15,700 km;
At the time of her design, she was not considered as being the forerunner of any class; she was designed by the Director of Naval Construction, Sir Nathaniel Barnaby, as a one-off as an answer to the French Amiral Baudin-class ironclads, which carried three heavy guns on the centreline and a number of smaller pieces on the broadside. He made several proposals to the Board of Admiralty, but they were all rejected. Barnaby's final submission was inspired by the four French Terrible-class ironclads laid down in 1877–78 and was a return to the configuration of Devastation with the primary armament positioned fore and aft of the central superstructure, but with the breech-loading main armament mounted in barbettes, as per the French ships, which allowed them to be sited 10 feet (3.0 m) further above the waterline than Devastation's guns. The Board modified Barnaby's design by adding 25 feet (7.6 m) of length and  2,000 indicated horsepower (1,500 kW) to guarantee a speed of 15 knots (28 km/h; 17 mph) at deep load. It also substituted four smaller 42-long-ton (43 t) guns for Barnaby's two 80-long-ton (81 t) guns. The additional length and the Board's acceptance of the hull lines from Colossus increased the size of the ship by 2,500 long tons (2,540 t).
Barnaby was severely criticised, particularly by Sir Edward Reed, himself a former Chief Constructor of the Royal Navy, because Collingwood's waterline armour belt was concentrated amidships and did not extend to the ends of the ship. Reed believed that this weakness meant that the ship could be sunk from the consequent uninhibited flooding if her unarmoured ends were riddled by shellfire and open to the sea. Barnaby deliberately selected a hull shape with narrow, fine ends to limit the volume of the hull that could be flooded and situated the armoured deck below the waterline to prevent it from being pierced by enemy shells and flooding the lower part of the ironclad. Furthermore, he heavily subdivided the hull to limit the amount of water that could enter through any one hit and placed coal bunkers above the armoured deck to absorb the fragments from exploding shells. Unbeknownst to his critics, Collingwood was tested in 1884 with her ends and the large spaces in her hold ballasted with water and her draught only increased by 17.5 inches (440 mm) and she lost a minor amount of speed. The price was that the ship lacked buoyancy at her ends and tended to bury her bow in oncoming waves rather than be lifted over them. Her speed was greatly reduced in a head sea and the resulting spray made working the guns very difficult. Collingwood tended to roll heavily and was not regarded as a good seaboat. Despite these issues, her basic configuration was followed by most subsequent British ironclads and predreadnought battleships until the revolutionary Dreadnought of 1905.
The ship had a length between perpendiculars of 325 feet (99.1 m), a beam of 68 feet (20.7 m), and a draught of 27 feet 10 inches (8.5 m) at deep load. She displaced 9,500 long tons (9,700 t) at normal load and had a complement of 498 officers and ratings.
The ship was powered by a pair of 2-cylinder inverted compound-expansion steam engines, each driving one propeller. The Humphreys engines produced a total of 7,000 indicated horsepower (5,200 kW) at normal draught and 9,600 ihp (7,200 kW) with forced draught, using steam provided by a dozen cylindrical boilers with a working pressure of 100 psi (689 kPa; 7 kgf/cm²). She was designed to reach a speed of 15.5 knots (28.7 km/h; 17.8 mph) at normal draught and Collingwood reached 16.6 knots (30.7 km/h; 19.1 mph) from 8,369 ihp (6,241 kW) on her sea trials, using natural draught. She was the first British ironclad to be equipped with forced draught and the ship only reached a speed of 16.84 knots (31.19 km/h; 19.38 mph) from 9,573 ihp (7,139 kW) while using it during her sea trials because her engines were incapable of handling the additional steam. Collingwood carried a maximum of 1,200 long tons (1,219 t) of coal that gave her a range of 8,500 nautical miles (15,700 km; 
HMS Collingwood (1882)