Horatio Nelson Lay (23 January 1832 – 4 May 1898, Forest Hill, Kent, England)[1] was a British diplomat, noted for his role in the ill-fated "Lay-Osborn Flotilla" during the Taiping Rebellion.

Lay's proficiency in the Chinese language soon earned him promotion in the British consular service and in 1854 he was appointed acting Vice-Consul in Shanghai.

Even though Lay was not in charge of designing the actual treaty, he was instrumental in intimidating the Qing delegation into signing it despite the highly unfavorable terms to the Chinese side.

During the Taiping Rebellion the Chinese government wished to regain control over Nanjing, which had been captured by the rebel forces in 1853 and declared their capital, but lacked the necessary ships to bring troops down the Yangtze River and to provide fire support.

[2] On 13 February 1863 the “Lay-Osborn” flotilla, also known as the Osborn or "Vampire" Fleet, with seven steam cruisers and a supply ship left England, arriving in China in September 1863.

The Imperial court refused to ratify this, and Osborn resigned in pique on 9 November 1863, disbanded the flotilla, and sent the ships back to England without them having fired a shot.