We have 1 night in Brussels! Our goal is to have moules-frite on the evening we arrive. We are staying at the Dominican Hotel so looking for a great restaurant within walking distance. Can anyone recommend? Thanks

Nothing near your hotel is recommendable for mussels.
Mussel season is from Sept to April, but, near the Grand Place it is always tourist plucking season, so you will find some.

Place Ste. Catherine has a bunch of seafood restaurants (it's the historic location of the fish trading docks)
La Belle Maraichere isn't too bad.

I can recommend other places if you decide to forego the mussels.

https://www.labellemaraichere.com/en/
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You would do better on the coast

Our local friends took to a fish market area and we ate fabulous mussels in a restaurant that specialized in them. Do not have the name, sorry.

The renowned restaurant Aux Armes de Bruxelles is just 2 minutes walk from your hotel, https://auxarmesdebruxelles.com/en
See walking map https://goo.gl/maps/z1dM31VqbAryKPB17
It does great nussels & frites.

July is early for mussels. Local mussels are not harvested from April until early July.

You are only supposed to have mussels in the months with a -r in their name (SeptembeR, OctobeR, etc). But since mussels is a tourist staple, as cdnyul says, you will find them somewhere.

I think Aux Armes de Bruxelles is a good choice as a restaurant with many Brussels dishes so if you don't have mussels, you can eat something else that is a local specialty. This is a better class of restaurant. I can also recommend a restaurant in the seafood area of the city, Ste.-Catherine, Noordzee-Mer du Nord. It is an outdoors dining venue with stand-up dining around barrels. Lots of fun. You could try the sea snails on their menu if they are in season.

You could also try Chez Léon in Rue des Bouchers, mussels features very prominently on their menu and it is their 'thing'. They are now a chain in other places as Léon de Bruxelles. This street used to be filled with rip-off restaurants but it has been cleaned up a bit and many, many restaurants here used to have mussels. Less formal dining than Aux Armes de Bruxelles, but if you are travelling with children it is a must as they cater for families.

Lastly, for an informal lunch there is the Wolf food court not far from you, just a few streets over. Not for mussels, just for an informal lunch near you. Lots of food choices there.

Lavandula

Local as in Dutch mussels?
The mussel harvest for Belgium is grown in Holland. The date of the first harvest varies a little each year. Belgium never runs out of mussels because it imports them from other countries when the dutch harvest has finished. Harvest has started for 2022. https://www.holland.com/global/touri...nd-mussels.htm
There are loads of reviews on where to eat them. Why the need to be within walking distance of your accommodations?
https://unravelog.com/cheatsheet/6-p...s-in-brussels/

cdnyul
good info! yes i forgot we are there off season for mussels. We love seafood so will take you up on other recommendations- ideally somewhere fairly close to our hotel area as we will walk (the one restaurant you did recommend looks like a nice menu!)