Thin-film　lithium　niobate　on　insulator　(LNOI)　is　a　promising　platform　for　optical　communications,　microwave　photonics,　and　quantum　technologies.　While　many　high-performance　devices　like　electro-optic　modulators　and　frequency　comb　sources　have　been　achieved　on　LNOI　platform,　it　remains　challenging　to　realize　photodetectors　(PDs)　on　LNOI　platform　using　simple　and　low-cost　fabrication　techniques.　2D　materials　are　excellent　candidates　to　achieve　photodetection　since　they　feature　strong　light-matter　interaction,　excellent　mechanical　flexibility,　and　potential　large-scale　complementary　metal–oxide–semiconductor-compatible　fabrication.　Herein,　this　demand　is　addressed　using　an　LNOI-2D　material　platform,　and　two　types　of　high-performance　LNOI　waveguide-integrated　2D　material　PDs,　namely　graphene　and　tellurium　(Te),　are　addressed.　Specifically,　the　LNOI-graphene　PDs　feature　broadband　operations　at　telecom　and　visible　wavelengths,　high　normalized　photocurrent-to-dark　current　ratios　up　to　3　×　106　W−1,　and　large　3-dB　photoelectric　bandwidths　of　≈40　GHz,　simultaneously.　The　LNOI-Te　PDs　on　the　other　hand　provide　ultrahigh　responsivities　of　7　A　W−1　under　0.5　V　bias　for　telecom　signals　while　supporting　GHz　frequency　responses.　The　results　show　that　the　versatile　properties　of　2D　materials　and　their　excellent　compatibility　with　LNOI　waveguides　could　provide　important　low-cost　solutions　for　system　operating　point　monitoring　and　high-speed　photoelectric　conversion　in　future　LNOI　photonic　integrated　circuits.　©　2023　The　Authors.　Advanced　Photonics　Research　published　by　Wiley-VCH　GmbH.