A　facile,　low-temperature　hydrothermal　synthetic　route　was　designed　for　fabricating　rutile　TiO2mesocrystals　composed　of　ultra-tiny,　rod-like　subunits.　Mesocrystals　with　tunable　sizes　and　morphologies　of　the　subunits　can　be　simultaneously　achieved　through　a　hydrothermal　re-treatment　process　at　different　temperatures.　A　probable　mechanism　for　the　formation　of　the　self-assembled　giant　rutile　TiO2mesocrystals　of　various　sizes　and　morphologies　is　proposed　based　on　the　experimental　results.　The　rutile　TiO2giant　mesocrystals　as-fabricated　were　also　tested　as　anode　materials　for　sodium-ion　storage,　and　exhibited　a　capacity　of　129.6 mA h g−1with　a　capacity　retention　of　97%　for　over　1000　cycles　at　a　charge–discharge　rate　as　high　as　5 C　and　enhanced　rate　capability　up　to　30 C　(64.5 mA h g−1at　30 C),　effectually　demonstrating　superior　sodium　storage　properties　in　terms　of　long-term　cycling　stability　and　rate　capability.　©　2016