HMS Iris was an Iris-class second-class cruiser of the Royal Navy. The Iris class ships were the first all-steel ships to serve with the Royal Navy and were employed as armed dispatch vessels. She had a double bottom and her Maudslay machinery produced , slightly less than her sister ship HMS Mercury, but her still made her one of the fastest ships of her day. Mercury was identical in most respects, though she had an upright stem and a different arrangement of head sail.