It is Samsung's equivalent of Apple's Siri and Google's Assistant - which is pre-installed already in Samsung phones as they run the Android operating system.
Bixby will initially be available in only two languages - US English and South Korean.
The launch had been delayed since April.
Samsung did not give a reason at the time but early testers of a limited demo model - including the BBC - had reported that it failed to understand commands.
The firm's latest device, the Galaxy Note 8, is due to be launched on 23 August.
What makes Bixby different from other voice assistants is that it is deeply integrated with functionalities unique to Samsung devices, said Ian Fogg, analyst at IHS Markit.
"Samsung always differentiates its phones by adding a lot of its own features to Android," he said.
These include tailored support for its own hardware such as the curved edge screen, stylus, VR support and camera.
Mr Fogg added that over time Bixby could also be included in other Samsung products which do not run on the Android operating system.
"A lot of people believe one voice agent will become the sole agent everyone will use," he said of the rivalry among the tech giants over digital assistants.
"But in life we don't have one single expert that we trust for everything. It might be they are good at different things.
"For the user it's just as easy to say Alexa, or Cortana, or Siri - there is no barrier to choosing an alternative voice agent."
However, he added that the technology will only be successful if it is dependable.
"To make it work you have to be able to understand speech reliably. If you don't do that nothing else happens. That should be a given".

A man approached her from behind and shoved her to the ground at about 13:30 GMT in Hanwell Cemetery, west London.
The suspect made off with her bag which was later recovered by a member of the public, but the purse had been taken.
The victim suffered minor injuries in the incident but did not require hospital treatment.
Police have released a CCTV image of the suspect, who is described as skinny, about 5ft 9in tall, wearing a black scarf covering his face, a grey hooded top, a black coat and jeans.
A Met Police spokesman said: "The robbery took place in broad daylight and police are keen to speak to members of the public who saw a man matching this description, walking briskly away from the scene, with his face covered and hood up."

Esther Kidemba died after apparently jumping from a building during a drill at the private Strathmore University in the capital, Nairobi.
Gunshots were fired during the drill, causing panic on the campus.
Militant Islamist group al-Shabab killed some 150 people in an attack on Garissa University College in April.
Strathmore University Vice-Chancellor John Odhiambo said he offered his deepest condolences to the family of Ms Kidemba, who was a staff member, and an "unreserved apology to every student, parent, family, colleague and stakeholder for the unfortunate outcome of the security drill".
Strathmore would pay for the medical expenses of 30 students and staff injured during the drill, and would arrange post-traumatic counselling, he added.
The drill had been carried out by the university's security team in co-ordination with local police to assess how they would deal with any attack, a statement by the university said.
On Monday, Nairobi police chief Japheth Koome said all the proper procedures had been followed for the mock security exercise, Reuters news agency reports.
But in his reaction, police chief Joseph Boinett said: "This must not happen again."
Kenya's security forces were on high alert to deal with threats, and drills should be conducted only with the authorisation of the "highest security office in the country", he added.
April's day-long assault on Garissa University College in north-eastern Kenya was the deadliest by al-Shabab in the East African state.
In 2013, at least 67 people were killed in an attack by the al-Qaeda-linked group, which is headquartered in neighbouring Somalia, on the upmarket Westgate shopping centre in Nairobi.
Al-Shabab says it is opposed to the presence of Kenyan troops in Somalia.
The troops are part of an African Union (AU) force helping the weak Somali government fight the militants who want to establish Islamic rule in the country.
Samsung's voice-controlled digital assistant Bixby is being rolled out in 200 countries from today.
[NEXT_CONCEPT]
A 73-year-old woman had her handbag snatched as she was cleaning her husband's grave on Christmas Eve, Met Police have said.
[NEXT_CONCEPT]
Kenya's police chief has warned universities not to carry out security drills without his approval following the death of a woman on Monday.