Lady Mary Hepburn-Stuart-Forbes-Trefusis (née Lygon; 26 February 1869 – 12 September 1927) was an English hymnwriter and courtier.

[4] Lady Mary was a friend and promoter of the composer Edward Elgar and is thought to be commemorated anonymously in one of his Enigma Variations entitled "Romanza (***)".

She directed a number of choirs, and together with Mary Wakefield was the joint founder of the National Association of Music Competition Festivals in 1904.

Trefusis proposed to Kerr that the remainder be spent buying a training centre for the Girl Guides, a cause close to the Princess's heart.

As the matter had to be settled by the next day, Kerr gave Trefusis the phone number of Pax Hill, the Baden-Powells' home.