Kalinga Magha or Gangaraja Kalinga Vijayabahu (Tamil: கலிங்க மாகன் / கலிங்க மாகோன் / கங்கராஜ காலிங்க விஜயவாகு மகன், Odia: କଳିଙ୍ଗ ମାଘ / ଗଙ୍ଗାରାଜ କଳିଙ୍ଗ ବିଜୟବାହୁ, Sinhala: කාලිංග මාඝ) was an invader from the Kingdom of Kalinga who usurped the throne from Parakrama Pandyan II of Polonnaruwa in 1215. A massive migration followed of Sinhalese people to the south and west of Sri Lanka, and into the mountainous interior, as they attempted to escape his power. Magha was the last ruler to have his seat in the traditional northern seat of native power on the island, known as Rajarata; so comprehensive was his destruction of Sinhalese power in the north that all of the successor kingdoms to Rajarata existed primarily in the south of the island.

Several theories exist about Magha, these theories range from defining him as an eastern Ganga king to a member of the Sinhalese Kalinga dynasty established by Kalinga Lokeshvara. Some historians identify him as the Kulankayan Cinkai Ariyan mentioned in the Jaffna Tamil chronicles, stating that Kulanka is actually a corruption of Kalinga. A Tamil inscription found in Gomarankadawala, Trincomalee District proves that Kalinga Magha was consecrated as King of Polonnaruwa under the name of Gangaraja Kalinga Vijayabahu by Kulothunga Chola III.

The exacts origin of Kalinga Magha is unknown, however due to his name, he is often referred to be from Kalinga, a historical place which corresponds mainly with present-day Odisha and northeastern Andhra. The most favoured theory states that Magha was a prince from the Eastern Ganga dynasty (Chodaganga) who ruled Kalinga. They were descended from the Kalinga Chandravanshi lineage and also from the Tamil Chola dynasty from the maternal side. Magha also seems to be related to the Kalinga branch of the Sinhalese Kingdom, and Nissanka Malla Deva of Polonnaruwa.

A late theory identifies Magha as the founder of the Jaffna kingdom and the first king of the Aryacakravarti dynasty. Many later Tamil works of Jaffna, mistake Kalinga Magha with the Aryacakravarti kings of Jaffna, who actually belong to the Aryacakravarti lineage of the Pandya Kingdom. The Cūḷavaṃsa, a Pali account, makes a clear distinction between Kalinga Magha, whom it describes as "the plague from the Kalinga that came with an army of Kerala mercenaries" and Arya Chakrawartin whom it describes as a Pandyan general.

The invasion of Kalinga Magha happened in a period of intense rivalry between two branches of the Sinhala royal family for the succession to the throne of Rajarata: the Arya branch which descended from Mithra (sister of king Vijayabahu I) who married a Pandyan prince and the Kalinga branch, descended from Vijayabahu I.

After the death of Parakramabahu I, who belonged to the Arya (or Pandya) branch, the country fall into the hands of foreign invaders both from Kalinga and Pandya dynasty. It is in this context of intense rivalry between Kalinga and Pandya dynasties, that Kalinga Magha, the "plague from Kalinga", (which was by then allied with the Chola dynasty) arrived in Lanka.

Kalinga Magha landed in Karainagar in 1215 AD with a large army of 24,000 Kerala and Tamil soldiers. He camped his soldiers in Karainagar and Vallipuram and brought the Jaffna principality under his control. Kalinga Magha then marched to Polonnaruwa, defeated Parakrama Pandyan II and ruled it for 21 years. He was expelled from Polonnaruwa in 1236 by a faction of Arya (Pandya) dynasty Sinhalese kings and withdrew to Jaffna with the Sinhalese throne which he ruled till 1255.

The Culavamsa, describes him as 'an unjust king sprung from the Kalinga line'.