List of Ubuntu Versions with Corresponding Linux Kernel Version

20.10   Groovy Gorilla    5.8
20.04   Focal Fossa       5.4
19.10   Eoan Ermine       5.3
19.04   Disco Dingo       5.0
18.10   Cosmic Cuttlefish 4.18
18.04   Bionic Beaver     4.15
17.10   Artful Aardvark   4.13
17.04   Zesty Zapus       4.10
16.10   Yakkety Yak       4.8
16.04   Xenial Xerus      4.4
15.10   Wily Werewolf     4.2
15.04   Vivid Vervet      3.19
14.10   Utopic Unicorn    3.16
14.04   Trusty Tahr       3.13
13.10   Saucy Salamander  3.11
13.04   Raring Ringtail   3.8
12.10   Quantal Quetzal   3.5
12.04   Precise Pangolin  3.2+
11.10   Oneiric Ocelot    3.0
11.04   Natty Narwhal     2.6.38
10.10   Maverick Meerkat  2.6.35
10.04   Lucid Lynx        2.6.32
09.10   Karmic Koala      2.6.31
09.04   Jaunty Jackalope  2.6.28
08.10   Intrepid Ibex     2.6.27
08.04   Hardy Heron       2.6.24
07.10   Gutsy Gibbon      2.6.22
07.04   Feisty Fawn       2.6.20
06.10   Edgy Eft          2.6.17
06.06   Dapper Drake      2.6.15
05.10   Breezy Badger     2.6.12
05.04   Hoary Hedgehog    2.6.10
04.10   Warty Warthog     2.6.8
 

• 16.04, 18.04, and 20.04 are the only currently supported releases (as of Aug 18, 2020).
• This lists the kernel version that ships with Ubuntu, but new minor versions may be installed during the Ubuntu installation if updates have been released since.

You can get the list of the Ubuntu versions and their corresponding kernels from Wikipedia:

4.10    Warty Warthog       2.6.8
5.04    Hoary Hedgehog      2.6.10
5.10    Breezy Badger       2.6.12
6.06    Dapper Drake        2.6.15
6.10    Edgy Eft            2.6.17
7.04    Feisty Fawn         2.6.20
7.10    Gutsy Gibbon        2.6.22
8.04    Hardy Heron         2.6.24
8.10    Intrepid Ibex       2.6.27
9.04    Jaunty Jackalope    2.6.28
9.10    Karmic Koala        2.6.31
10.04   Lucid Lynx          2.6.32
10.10   Maverick Meerkat    2.6.35
11.04   Natty Narwhal       2.6.38
11.10   Oneiric Ocelot      3.0
12.04   Precise Pangolin    3.2 or newer
12.10   Quantal Quetzal     3.5
13.04   Raring Ringtail     3.8
13.10   Saucy Salamander    3.11
14.04   Trusty Tahr         3.13 or newer
14.10   Utopic Unicorn      3.16
15.04   Vivid Vervet        3.19
15.10   Wily Werewolf       4.2
16.04   Xenial Xerus        4.4 or newer
16.10   Yakkety Yak         4.8
17.04   Zesty Zapus         4.10
17.10   Artful Aardvark     4.13
18.04   Bionic Beaver       4.15 or newer
18.10   Cosmic Cuttlefish   4.18
19.04   Disco Dingo         5.0
19.10   Eoan Ermine         5.3
20.04   Focal Fossa         5.4 
20.10   Groovy Gorilla      5.8

Take a look at this version table or this directory listing. I think that is what you are interested in.