Phosphors have been used successfully for both research and commercial applications for decades. Eu3+-doped materials are especially promising, because of their extremely stable, efficient, and narrow red emission lines. Although these emission properties are ideal for lighting applications, weak absorption in the blue spectral range has until now prevented the use of Eu3+-based phosphors in applications based on blue light-emitting diodes. Here, we demonstrate a sensitization mechanism of Eu3+ based on interparticle Förster resonance energy transfer (IFRET) between lanthanide-doped inorganic nanocrystals (NCs). Compared to co-doping different lanthanides in the same host crystal, IFRET allows an independent choice of host lattices for Eu3+ and its sensitizer while potentially greatly reducing metal-to-metal charge transfer quenching. We demonstrate IFRET between NCs, resulting in red Eu3+ emission upon blue excitation at 485 nm using LaPO4:Tb/LaPO4:Eu and LaPO4:Tb/YVPO4:Eu NC mixtures. These findings pave the way toward engineering blue-sensitized line emitters for solid-state lighting applications.