| Raja Lumu Secondary School | |
| Motto: | Bersama Berilmu Berkualiti Berwawasan |
| Established: | 1982 |
| Type: | Secondary school |
| Session: | Single + 2 |
| Principal: | Miss Noreha Hailani |
| District: | Klang |
| City: | Port Klang |
| State: | Selangor |
| Country: | Malaysia |
| Colours: | White, Yellow, Red |
SMK Raja Lumu (or Raja Lumu Secondary School) is a secondary school in Port Klang, Selangor, Malaysia established in 1982.
The school's land was originally planned for Simpang Lima Tamil Primary School. But because of the location, the school was closed and became Putera Sekolah Tengku Ampuan Rahimah. Then, the school has moved to a new location and here became the hostel for Putera Sekolah Tengku Ampuan Rahimah dan Pulau Lumut. After it was renovated for a few years, the Raja Lumu Secondary School was established.
On 1 January 1982, Mr. Mohammad Noribinin Taib was appointed to be the school's first principal and Mrs. S. Sthipam as the supervisor of this school.
This school holds 2 schooling sessions. The morning session is for Form 3, Form 4 and Form 5 (ages 15 to 17) while the afternoon session is for Peralihan or Reform students, Form 1 and Form 2 students (ages 13 to 14). This is done to accommodate the large number of students attending the school. A former school studies group was made in the class 5 Saga in the year 2023 under the name "Yu Yang Quintuplets" (now named Persatuan Cina Sejati or Persatuan Durian). The elite study group consists of 5 Malay-Chinese students and 1 Bumiputera student.