Family name Illangakoon (Illangakoon 
) , all over the world, is quite a rare surname. The family name Illangakoon is habitual in Sri Lanka, where it is quite a common surname, Australia, where it is a very rare surname, and Canada. In absolute terms, it most frequently occurs in Sri Lanka, Australia, and the United States.
| VARIANT | COUNTRY |
|---|---|
| Illangakoon | Sri Lanka, United Kingdom, Australia, Canada, United States |
| nugagaha kapalle illangakoon LK (b. 1956) |
|
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| john william ronald illangakoon john William Ceylon Lawyer |
|
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| j. w. r. illangakoon |
|
Don, Dulhari, Thanuja, Thilina, Indunil, Ineshika, Uthpala, Sanjeewa, Samanthi, Shashika, Dorothy, Achintha, Kanchana, Pabasara, Rakhitha, Lasantha, Wasantha, Thushanee, Vikasitha, Mahamanna Liyanage Manori, Sathsarani, Charitha, Praneeshan, Kushaal, Ashvini, Sabi, Amal, Manoj, Mahes, Sanka, Anita, Beryl, Rohan, Gayan, Chaturi, Lakna, Mervyn, Sumeda, Sugath, Achala, Achira, Gamini, Janith, Eranka, Manjula, Madura, and Ralph Joseph Anil