Species Recorded | Taxon | Scientific Name | Common Name | Records | Latest |
| ant, bee, wasp, sawfly or ichneumon (and others) | Zatypota bohemani | an ichneumon wasp | 1 | 2003 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Zatypota percontatoria | an ichneumon wasp | 1 | 2002 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Zele chlorophthalmus | a braconid wasp | 6 | 2023 |
| beetle | Zacladus geranii | Meadow Cranesbill Weevil | 13 | 2020 |
| bird | Zapornia parva | Little Crake | 1 | 1986 |
| bristletail (silverfish and allies) | Zygentoma | a Thysanura species (unidentified) | 3 | 2008 |
| bug | Zicrona caerulea | a shield bug | 23 | 2023 |
| bug | Zygina | a Zygina species (unidentified) | 1 | 2013 |
| bug | Zygina angusta | a leafhopper | 1 | 2020 |
| bug | Zygina flammigera | a leafhopper | 5 | 2020 |
| bug | Zygina hyperici | a leafhopper | 2 | 2022 |
| bug | Zyginella pulchra | a leafhopper | 1 | 2008 |
| bug | Zyginidia scutellaris | a leafhopper | 4 | 2010 |
| dragonfly, hawker or damselfly | Zygoptera | a damselfly (unidentified) | 423 | 2021 |
| fish | Zeugopterus punctatus | Topknot | 2 | 1938 |
| fish | Zeus faber | John Dory | 3 | 1938 |
| mollusc | Zenobiellina subrufescens (J. S. Miller, 1822) | Brown Snail | 19 | 2020 |
| mollusc | Zonaria | a Zonaria species (unidentified) | 1 | 2004 |
| mollusc | Zonitidae | a Zonitidae species (unidentified) | 1 | 1992 |
| mollusc | Zonitoides (Zonitoides) nitidus | Shiny Glass Snail | 7 | 2004 |
| moss | Zygodon | a Zygodon species (unidentified) | 1 | 2004 |
| moss | Zygodon conoideus | Lesser Yoke-moss | 13 | 2023 |
| moss | Zygodon rupestris | Park Yoke-moss | 3 | 2003 |
| moss | Zygodon viridissimus | Green Yoke-moss | 38 | 2023 |
| moss | Zygodon viridissimus (sens.lat.) | a moss | 1 | 2017 |
| moss | Zygodon viridissimus var. viridissimus | a green yoke-moss | 10 | 2018 |
| moth or butterfly - macro moth | Zeuzera pyrina | Leopard Moth | 164 | 2022 |
| moth or butterfly - macro moth | Zygaena | a burnet moth (unidentified) | 71 | 2021 |
| moth or butterfly - macro moth | Zygaena filipendulae | Six-spot Burnet | 877 | 2023 |
| moth or butterfly - macro moth | Zygaena filipendulae filipendulae | a Six-spot Burnet | 1 | 2014 |
| moth or butterfly - macro moth | Zygaena filipendulae stephensi | a Six-spot Burnet | 26 | 2023 |
| moth or butterfly - macro moth | Zygaena lonicerae | Narrow-bordered Five-spot Burnet | 244 | 2023 |
| moth or butterfly - macro moth | Zygaena lonicerae latomarginata | a narrow-bordered five-spot burnet | 89 | 2009 |
| moth or butterfly - macro moth | Zygaena lonicerae/trifolii | Narrow-bordered five-spot or Five-spot Burnet (undetermined) | 121 | 2019 |
| moth or butterfly - macro moth | Zygaena trifolii | Five-spot Burnet (form unknown) | 8 | 2023 |
| moth or butterfly - macro moth | Zygaena trifolii trifolii | a Five-spot Burnet | 1 | 2023 |
| moth or butterfly - micro moth | Zeiraphera griseana | Larch Tortrix | 1 | 2020 |
| moth or butterfly - micro moth | Zeiraphera isertana | Cock's-head Bell | 39 | 2023 |
| moth or butterfly - micro moth | Zeiraphera ratzeburgiana | a tortrix moth | 17 | 2021 |
| moth or butterfly - micro moth | Zelleria hepariella | a micro-moth | 26 | 2022 |
| plant | Zannichellia palustris | Horned Pondweed | 114 | 2016 |
| plant | Zannichellia palustris subsp. palustris | a Plant | 1 | 2010 |
| plant | Zannichellia palustris subsp. pedicellata | Stalked-fruited Horned Pondweed | 1 | 1920 |
| plant | Zantedeschia aethiopica | Altar-lily | 3 | 2011 |
| plant | Zauschneria californica | a Plant | 3 | 2005 |
| plant | Zea mays | Maize | 15 | 2016 |
| plant | Zelkova serrata | Keaki | 2 | 2015 |
| plant | Zingeria pisidica | a Plant | 1 | 1940 |
| plant | Zostera (Zostera) marina | Eelgrass | 4 | 2017 |
| reptile | Zootoca vivipara | Common Lizard | 413 | 2023 |
| spider | Zelotes | a Zelotes spider (unidentified) | 6 | 1999 |
| spider | Zelotes apricorum | a ground spider | 2 | 1989 |
| spider | Zelotes apricorum/subterraneus (sens.lat., sensu Bristowe, 1939) | a ground spider | 1 | 1989 |
| spider | Zelotes latreillei | a ground spider | 5 | 1999 |
| spider | Zilla diodia | an orb-weaver spider | 5 | 2023 |
| spider | Zora spinimana | a ghost spider | 6 | 1998 |
| spider | Zygiella | a Zygiella species (unidentified) | 4 | 2023 |
| spider | Zygiella atrica | Red-sided Sector Spider | 3 | 2017 |
| spider | Zygiella x-notata | Missing Sector Orb Weaver | 41 | 2023 |
| true fly - | Zophomyia temula | a parasitic fly | 8 | 2013 |
| true fly - (diptera) | Zygoneura sciarina | a fly | 1 | 2021 |
| true fly - midge, gnat or mosquito | Zygiobia carpini | a gall midge | 1 | 1994 |
| true fly - midge, gnat or mosquito | Zygomyia pictipennis | a fungus gnat | 3 | 2000 |
| true fly - midge, gnat or mosquito | Zygomyia valida | a fungus gnat | 5 | 2021 |
| true fly - midge, gnat or mosquito | Zygomyia vara | a fungus gnat | 1 | 2000 |