The first parallel algorithm to accelerate the Smith-Waterman protein database search on shared-host multiple Intel Xeon Phi coprocessors. By searching against the UniProtKB/TrEMBL database, SWAPHI achieves a performance of up to 58.8 billion cell updates per second (GCUPS) on a single Xeon Phi and up to 228.4 GCUPS on four Xeon Phis.