| Thirumazhisai | |
| Settlement Type: | Neighborhood |
| Pushpin Map: | India Chennai#Tamil Nadu#India |
| Pushpin Label Position: | left |
| Pushpin Map Caption: | Thirumazhisai (Chennai) |
| Coordinates: | 13.0525°N 80.0603°W |
| Subdivision Type: | Country |
| Subdivision Name: |  India |
| Subdivision Type1: | State |
| Subdivision Name1: | Tamil Nadu |
| Subdivision Type2: | District |
| Subdivision Name2: | Thiruvallur |
| Subdivision Type3: | Metro |
| Subdivision Name3: | Chennai |
| Unit Pref: | Metric |
| Area Total Km2: | 34.1 |
| Elevation M: | 54 |
| Population Total: | 52334 |
| Population As Of: | 2011 |
| Population Density Km2: | auto |
| Demographics Type1: | Languages |
| Demographics1 Title1: | Official |
| Demographics1 Info1: | Tamil |
| Timezone1: | IST |
| Utc Offset1: | +5:30 |
| Postal Code Type: | PIN |
| Postal Code: | 600 124 |
| Registration Plate: | TN 12 (RTO, Poonamallee) |
Thirumazhisai is a western suburb of Chennai, India. It is located in Thiruvallur district of Tamil Nadu. Located on the way to Thiruvallur, the neighbourhood is situated at a distance of 28 km from the city's kilometer zero. The nearest railway station is at Thiruninravur, which is 13 km away.
The neighbourhood is the birthplace of Thirumalisai Alvar, one of the 12 Vaishnavite poet-saints of the Bhakti era.