France, Australia, Peru and Denmark make up Group C, with Group D perhaps the closest to a so-called "Group of Death" as it contains Argentina, Iceland, Croatia and Nigeria.
"They're an outstanding team", Southgate said of Roberto Martinez's side.
They will then travel to Nizhny Novgorod on June 24 to take on Panama, with their final group fixture against Belgium on June 28 in Kaliningrad.
With Belgium able to call upon Premier League stars such as Chelsea's Eden Hazard, Manchester City's Kevin de Bruyne and Romelu Lukaku at Manchester United, they are now ranked fifth in the world, 10 places higher than England.
Southgate feels the current Belgium squad is the best the country has ever produced, and calls the draw "really exciting".
"They're the top seeds in the group, but a really good challenge for us".More news: European data watchdogs go after Uber
"We've obviously not been following their games in our qualifying phase".
"Panama, we've never played, and Tunisia have qualified through the African group, which is strong, so they're to be respected".
With all this considered, it's now high time we had a peek at what England's players (might?) be wearing as they take to the field in Russian Federation.
Elsewhere in the draw, Spain were placed in the same group as Portugal, alongside Morocco and Iran, while five-time winners Brazil have to negotiate a group including Switzerland, Costa Rica and Serbia.
Argentina have been paired with debutants Iceland, Croatia and Nigeria in Group D.
"We're the second-ranked team in that group so it's understandable how people will pitch it but, equally, in the last two tournaments we went out to teams we thought we'd beat".