Is There a "Medal of Honor 4" for PSP? No—Only Heroes and Heroes 2

No. There is no game titled "Medal of Honor 4" on any platform. The PSP received two main entries:

1. Medal of Honor: Heroes (2006) – First PSP entry. Single-player campaign + Ad-hoc multiplayer (up to 32 players via infrastructure mode patch).
2. Medal of Honor: Heroes 2 (2007) – Improved graphics, online infrastructure multiplayer (32 players), Wii version released simultaneously (different controls).

Other PSP appearances:

• Medal of Honor: Infiltrator (GBA, not PSP).
• Medal of Honor: Allied Assault (PC/PS2/Mac only).

The mainline numbering (Allied Assault → Pacific Assault → Airborne → 2010 → Warfighter → Above and Beyond) skipped PSP. Heroes and Heroes 2 are the portable sub-series.