Willie Tan Ong (Chinese: 許偉利; Pe̍h-ōe-jī: Khó͘ Úi-lī; pinyin: Xǔ Wěilì;[3] born October 24, 1963) is a Filipino cardiologist, internist and media personality who rose to prominence for giving medical advice through his Facebook page and YouTube channel.

Ong was also a candidate for the 2019 Philippine Senate election, largely capitalizing on his social media presence.

He was a candidate for vice president in the 2022 Philippine presidential election as the running mate of former mayor of Manila Isko Moreno.

Better known as Co Tec Tai (許澤台) in the Chinese Filipino community,[3] the elder Ong was an active charity worker who served as president for various civic organizations.

He also achieved the award for the highest academic performance when he earned his Masters in Public Health at the University of the Philippines Manila.

[6] Ong was also a resident doctor and host at DZRH's public service program Docs on Call from 2009 to 2017.

[9] Ong started maintaining an online presence when he set up a YouTube channel in 2007, where he posts videos providing health tips and medical explainers targeted to a general audience.

[13] Outside of health issues, Ong also expressed openness for the introduction of death penalty for heinous crimes, the lowering of the minimum age of criminal responsibility, and the adoption of federalism as the form of government for the Philippines.

[14] Running on the banner of the Lakas–CMD political party, Ong said he did not rely on campaign donations to "avoid being indebted to anyone".

[18] Despite undergoing treatment for cancer in Singapore, Ong filed his certificate of candidacy for senator on October 3, 2024 for the 2025 Philippine elections through his wife, Anna Liza Ramoso.

[24] With his brother's help, Ong had gone to Singapore to undergo treatment at Parkway East Hospital under oncologist Ang Peng Tiam.