In　this　paper,　we　report　the　development　of　rare-earth　high-entropy　alloys　(RE-HEA)　with　multiple　principle　elements　randomly　distributed　on　a　single　hexagonal　close-packed　(HCP)　lattice.　Our　work　demonstrated　that　it　is　the　entropy,　rather　than　other　atomic　factors　such　as　enthalpy,　atomic　size　and　electronegativity,　that　dictates　phase　formation　in　the　current　rare-earth　alloy　system.　The　high　configuration　entropy　stabilized　the　crystalline　structure　from　phase　transformation　during　cooling,　whereas　a　second-order　magnetic　phase　transition　occurred　at　its　Neel　temperature.　The　quinary　RE-HEA　exhibited　a　small　magnetic　hysteresis　and　the　largest　refrigerant　capacity　(about　627　J　kg(-1)　at　the　5　T　magnetic　field)　reported　to　date,　along　with　respectable　mechanical　properties.　Our　analysis　indicates　that　the　strong　chemical　disorder　resulted　from　the　high　configuration　entropy　makes　magnetic　ordering　in　the　HEA　difficult,　thus　giving　rise　to　a　sluggish　magnetic　phase　transition　and　enhanced　magneto　caloric　effect.　Our　findings　evidenced　that　RE-HEAs　have　great　potential　to　be　used　as　magnetic　refrigerants　and　the　alloy-design　concept　of　HEAs　can　be　employed　to　develop　novel　high-performance　magnetocaloric　materials.　(C)　2016　Acta　Materialia　Inc.　Published　by　Elsevier　Ltd.　All　rights　reserved.