The postal code 100001 is designated for the General Post Office (GPO) in Ikeja, the capital of Lagos State, Nigeria. In Nigeria, main post offices in each region have postal codes ending in 0001.
The Nigerian Postal Service (NIPOST) divides the country into nine regions, with the first digit of the postal code representing the region. The subsequent digits help in sorting and delivery within specific areas. Therefore, 100001 serves as the primary postal code for Ikeja’s main postal facility.
| Place/Area | Postal Code |
| Amuwo Odofin | 100001 |
| Ikeja | 100001 |