The French Navy commissioned Iris on 31 December 1808, under capitaine de fregate Charles Méquet (or Joseph-Jean Macquet, or Miquet).

[3] En route, on 2 February at 11am she encountered HMS Aimable, under Captain Lord George Stuart, while off the Texel on the Wellbank.

Lloyd's List reported that she had been captured on 4 February, and that at the time of the encounter she had been in company with a brig.

There the Royal Navy took her into service as HMS Rainbow and proceeded to fit her out until 23 August.

[2] On 13 March 1810, Rainbow encountered the French frigate Néréide, under the command of Jean-François Lemaresquier, off Point Abaco.

Lemaresqueir continued to flee to separate the two British ships, but stopped to engage Rainbow after Avon had fallen back.

He soon had reduced Rainbow to a battered state, but Avon resolutely came in support and put a 30-minute fight against the much stronger Néréide before herself retreating.

[10][a] Rainbow and Pylades were in company on 18 June searching for a "remarkably fast-sailing brigantine", of one gun and 40 men.

[14] Next, on 13 December, Hamilton went onshore to assist the Italian levies in their unsuccessful attack on Leghorn.

[16] In April 1814 Rainbow supported the British Army in its successful attack on Genoa, losing one man severely wounded.

[17] Before the fall of Genoa, the boats of Berwick and Rainbow, together with two Sicilian gunboats, attacked French posts near the pass of Rona on 8 and 10 April to assist the British Army in its advance.