Valerie Smith, wife of the late legendary trainer Tommy Smith and mother of champion Sydney trainer Gai Waterhouse, has died in Sydney at the age of 91.

Val Smith had been ill for some time and died early on Wednesday.

Her daughter and son-in-law Robbie Waterhouse, the leading Sydney bookmaker, are overseas and will cut short their annual holiday to return to Sydney.

"Mum left our home today, never to return," Waterhouse reported on her website.

"Darling, we'll miss you hugely. Rest well, I promise to train lots of winners.

"Thanks Mum for all your time showing me the ropes and just loving me."

Tommy Smith died in 1998.