Variants
Model 7A   Prototype
Model 7B   Second prototype
DB-7   Initial production version (70 built) 
DB-7B   All aircraft built delivered to Great Britain, designated Douglas Boston Mk III  self sealing fuel tanks, additional armor, enhanced structural strength, a longer fuselage for a more glazed bombardiers nose and more fuel capacity (781 built)
DB-7C   Dutch version of the DB-7B, fitted with interchangeable nose (glazed bombardier or solid with 4 × 20 mm cannons) and special racks suited for carrying a torpedo (20 built)
A-20 Havoc   Based on DB-7B version, self sealing tanks, strengthened structure, and a more extensively glazed nose (1  built)
A-20A   New engines (143 built) 
A-20B   New engines, could carry ferry fuel in weapons bay, nose glazing, increased bombload, more or less equivalent to Boston Mk II (999 built)
A-20C   Equivalent to Boston Mk III, American guns and different exhausts on the engines (948 built)
A-20E   New engines (17 built) 
A-20G   Stripped of dual controls, added extra armor and carburetor de-icing, built in several blocks: 
:A-20G-1 (200 built) 
:A-20G-5 (50 aircraft)
:A-20G-10 (300 aircraft), improved carburetor air inlets 
:A-20G-15 (150 aircraft), improved heating for winter operations 
:A-20G-20 (350 aircraft), widened rear fuselage for the electical Martin dorsal turret with 2 × 12.7mm  guns 
:A-20G-25 (399 aircraft), winter version of the A-20G-20 
:A-20G-30 (353 aircraft), improved spent-cartridge collection system 
:A-20G-35 (328 aircraft), heavier gauge skinning on the tailplane 
:A-20G-40 (380 aircraft), modified engine exhaust system, revised cowlings, upgraded navigation system 
:A-20G-45 (290 aircraft), winter version of the A-20G-40 
Number built: 2.850 
A-20H   Similar to A-20G-45, but with new engines (412 built) 
A-20J   Similar to A-20G-25, but with a plexiglas frameless bomber nose, featuring a bombsight, 169 to RAFas Boston Mk IV (450 built)
A-20K   Similar to A-20J with the airframe/powerplant combo of the A-20H (413 built)
F-3A   Reconnaissance aircraft, based on the A-20 (88 buyilt) 
P-70A-1   Conversions of A-20C Attack bomber . Improved radar, and 6 or 8 × 0.50 in (12,7 mm) fixed forward firing guns in a ventral pack (39 built)
P-70A-2 Conversions of the A-20G Attack bomber, similar to the F-70A-1 (65 built)
P-70B   Conversions for training purposes, with American radar equipment 
P-70B-1   A-20G-10 conversion. Centimetric radar, 6×12.7mm guns in blisters around nose (1 built)
P-70B-2   A-20G and A-20J conversions, with centimetric radars (105 built)
CA-20G   Converted from the A-20J to act as a high speed transport after the War. 
TA-20H   A-20H Havocs converted for training. 
TA-20J   A-20J Havocs converted for training. 
TA-20K   A-20K Havocs converted for training. 

RAF
Boston Mk I   Some 20 French and 16 Belgian DB-7's were taken over by the UK after the capitulation of both countries. Converted to UK standards, designated Boston Mk I and used for training purposes (36 built)
Boston Mk III Redesignated DB-7B's. 
Boston Mk III (Intruder)   Boston Mk III's revised as intruders, ventral pack fitted with ? × 20 mm cannons and reduced bomb load of 1,000 lb
Boston Mk III (Turbinlite)   Boston Mk III revised in same fashion as Havoc Mk I and II (Turbinlite) versions (3 built)
Boston Mk IIIA   British A-20C Havocs, with British guns and equipment (200 delivered to RAF) 
Boston Mk IV   169 A-20Js, delivered to the RAF, and redesignated Boston Mk IV 
Boston Mk V   90 A-20K's, delivered to the RAF, and redesignated Boston Mk V
Havoc Mk I (Intruder)   Remainder of French DB-7 aircraft, put to use as home-defense night-fighters and intruders.
changed to British equipment and weapons, flame-damper exhausts, and improved armor protection (181) 
Havoc Mk I (Night-Fighter)   Equal to Intruder version, except for the crew (2), the AI.Mk IV radar, and non standard armament of 8 × 0.303 in fixed forward firing machine guns 
Havoc Mk I (Pandora)   Equal to Intruder version, but fitted with LAM (Long Aerial Mine) systems (20 built)
Havoc Mk I (Turbinlite)   Equal to the Intruder version, noses replaced by a 2,700 candlepower searchlight (21 built) 
Havoc Mk II   French ordered aircraft, based on DB-7A, new engine, modified landing gear, structural strengthening and a larger vertical tail surface, 1 additional rearward firing 0.295 in machine gun in each of the engine nacelles, none reached France before it's capitulation and weresent to UK (100 built)
Havoc Mk II (Turbinlite)   Equal to the Intruder version, noses replaced by searchlight (39 built)