The poem ‘In Memoriam’ is written by-

The poem ‘In Memoriam’ is a great elegy written by Alfred Tennyson to commemorate the death of his friend Arthur Henry Hallam.

The other notable poems of Tennyson are:
The Lotos Eaters
-‘Morte D’ Arthur’
-‘Oenone’
-‘Locksley Hall’
-‘Ulysses’
-‘Tithonus’.
Source: Britannica.com