Metamaterials　based　on　quasi-bound　states　in　the　continuum　(qBICs)　with　manipulable　resonance　quality　(Q)　factors　have　provided　a　standout　platform　for　cutting-edge　terahertz　(THz)　sensing　applications.　However,　most　so　far　have　been　implemented　as　conventional　metal　patch　structures　with　adjacent　substrate　layers,　incurring　the　limitation　of　insufficient　light-matter　interaction　due　to　substrate　effects.　Here,　qBIC-driven　metamaterials　with　substrate-free　metallic　aperture　structures　for　tailoring　light-matter　interactions　and　exhibiting　near-ideal　sensing　performance　is　introduced.　Specifically,　it　is　incorporated　ultrafast　femtosecond　laser　processing　technology　to　fabricate　H-type　metallic　aperture　metamaterials　with　accessible　high-contrast　Q　factor　resonances　allowed　by　in-plane　symmetry　breaking.　Correspondingly,　stronger　light　field　energies　are　applied　to　the　interactions　due　to　completely　eliminating　the　confinement　of　the　substrate　effect,　enabling　experimental　sensitivity　of　up　to　0.86　THz　RIU-1　for　the　qBIC　resonance,　1.9　times　that　of　the　conventional　dipole　resonance.　Moreover,　a　high　Q　qBIC　resonance　achieved　by　optimized　asymmetry　parameter　is　exploited　for　detecting　ultrathin　layers　of　L-proline　molecules　as　low　as　0.87　nmol.　It　is　envisioned　that　this　approach　will　deliver　insights　for　real-time,　precise,　and　high-performance　detection　of　trace　biomolecules,　and　open　new　perspectives　for　realizing　ideal　performance　metadevices.　A　BIC-driven　substrate-free　terahertz　metamaterial　sensor　is　developed　to　completely　overcome　the　limitation　of　insufficient　light-matter　interaction　due　to　substrate　effects.　The　experimental　results　report　a　sensing　sensitivity　up　to　0.86　THz　RIU-1　and　exploit　the　tunable　characteristic　of　the　qBIC　resonance　to　customize　the　structural　configuration　for　different　detection　scenarios.　image