The former British No 1 posted a link on her Twitter page, saying: "I have some news to share with you." In a fuller statement released on the Lawn Tennis Association website), the 30-year-old then said: "I have recently been diagnosed with cancer of the liver. I'm currently undergoing treatment and fighting this illness with everything I have."
Baltacha and her husband Nino also thanked the public for their continued support.
The star was born in Ukraine and has represented Scotland, but says she considers herself British. Plagued by ill health and injury, at the age of 19 she was diagnosed with primary sclerosing cholangitis, a chronic liver condition which compromises the immune system.
Andrew Langford, chief executive of the British Liver Trust, said she would have known for a while that she was at risk of liver cancer because of her condition.
He said: "It is a genetic illness that infects your bile duct. You get a back flow of bile into your liver and that causes scarring in your liver. As the liver is more scarred it will be so damaged that you will have cirrhosis.
"Normally when we talk about liver cirrhosis people think about alcohol, but this is definitely not related to alcohol.
"I would imagine she will have a range of treatments. It will be a very difficult time for her and it may be that she eventually needs to have a liver transplant."
According to the British Liver Trust, primary liver cancers - those that start in the liver - are rare in the UK, making up about 1% of all cancers and affecting about 3400 people.
Tennis coach Judy Murray was among the sports stars to wish the sportswoman - who is known by her nickname 'Bally' - well.
She said: "Obviously this is a tough time for Bally, Nino and her family, but she is a such a determined, upbeat person and everyone around her is staying positive as well.
"I know she will be really grateful for all the support she is getting."
Her former team-mate Anne Keothavong posted a picture online of the two players together and said: "She is one of the people I most admire for her courage and determination. You will fight through this."
British No. 4 Tara Moore said Baltacha was a "great mentor and someone I look up to greatly. You will fight this, we are all behind you."
Television presenter Andrew Castle, also a former British No. 1, said: "Passing on love and best wishes to Elena Baltacha for a speedy recovery. Shocked by this news."
Baltacha announced her retirement last November, saying at the time that her body no longer allowed her to compete at the top level.
Born in Kiev, she grew up in Perth where her footballer father Sergei played for St Johnstone and later became the highest-ranked female singles player Scotland has ever produced.
She ranked No. 1 for Great Britain for 132 weeks between 2009 and 2012 and at her peak held a career-high ranking of 49, twice reaching the third round of the Australian Open and making the same stage of Wimbledon in 2002.
In December last year Baltacha married long-term boyfriend and coach Nino Severino and the couple now run the Elena Baltacha Academy Of Tennis together in Ipswich.
On the same day the tennis star announced her illness, she also reached out to fans via her academy's Facebook page to support the Children's Liver Disease Foundation, of which she is a patron.
A spokeswoman for the charity said Baltacha was a "great inspiration and role model for young people with liver disease" and wished her all the best.
The news comes after British tennis player Ross Hutchins, a close friend of Andy Murray, returned to the sport earlier this year after recovering from Hodgkins Lymphoma.
The 29-year-old Davis Cup player was diagnosed with the illness in December 2012 but announced last July he was in remission.