In the disturbing 36-second clip, the girls, aged 15 and 16, can be seen violently flinging the eight-week-old animal at each other in a bedroom at one of their homes on the Isle of Sheppey, Kent.
They can be heard giggling uncontrollably as the kitten appears to be knocked unconscious after hitting the ceiling.
The callous teenagers were fined £85, given a nine-month referral order and disqualified from keeping animals for a year after admitting causing unnecessary suffering to a kitten at Maidstone Youth Court.
RSPCA chief inspector Steve Dockery said: "This was shocking footage of young girls violently throwing an eight-week-old kitten around.
"The girls' commentary on the video shows that they found their actions to be hilariously funny, which is worrying.
"The abuse of a young animal purely for entertainment cannot be tolerated and posting it on a social networking site sends out a message that animal cruelty is acceptable.
"The kitten was lucky to survive her ordeal and has since been re-homed with a new and loving family."
The teenagers, who must also pay £85 each in court costs, were caught after a member of the public spotted their video on Facebook and reported it to the police.
A vet who examined the kitten after her ordeal in August said she would have suffered massive distress and it was a miracle she had not sustained severe physical injuries.
A third girl, aged 16, who is accused of filming the attack, pleaded not guilty and is due to be tried later in the year.
You can watch the video footage below - but some readers may find it upsetting.