The 2025 3. deild karla (English: Men's Third Division) was the 71th season of fourth-tier Icelandic football. The season began on 3 May and finished on 13 September 2025.
The title winners (HvÃÂti Riddarinn) and runners-up (Magni) were promoted to the 2026 2. deild karla, whilst the bottom two teams (KFK Kópavogur and ÃÂH) were relegated to the 2026 4. deild karla.
The league consisted of twelve teams; eight teams remaining from the previous season, two teams promoted from the 4. deild karla, and two teams relegated from the 2. deild karla.
The promoted teams were 2024 4. deild karla champions Tindastóll and runners-up IH (replacing the 2024 3. deild karla relegated teams EllÃÂði and Vængir Júpiters). The relegated teams were 2024 2. deild karla bottom two teams KF and Reynir (replacing the 2024 3. deild karla promoted teams Kári and VÃÂðir).
Each team played each other twice (22 matches each), once at home and once away.