William Arden, 2nd Baron Alvanley (8 January 1789 – 16 November 1849) was a British Army officer, peer and socialite, who was a friend of Beau Brummell and one of a close circle of young men surrounding the Prince Regent.

[4] Lord Alvanley was a prominent Regency buck and member of the Prince Regent's circle, and was friends with Beau Brummell.

They were also the four hosts of the July 1813 masquerade ball at which the Prince Regent greeted Alvanley and Pierrepoint, but then "cut" Brummell and Mildmay by snubbing them, staring them in the face but not speaking to them.

The Prince Regent was not amused; this incident was the final and most public sign that Brummell was no longer favored by "Prinny".

According to a near contemporary report, "[Alvanley] went through the business with the most perfect sang froid, but on his way to the field he whimsically intimated a singular alarm.