diff --git a/changelog.txt b/changelog.txt
index 8b0e5af951..9fd829a285 100644
--- a/changelog.txt
+++ b/changelog.txt
@@ -31,6 +31,7 @@ Template for new versions:
 - `uniform-unstick`: (reinstated) force squad members to drop items that they picked up in the wrong order so they can get everything equipped properly
 - `gui/reveal`: temporarily unhide terrain and then automatically hide it again when you're ready to unpause
 - `gui/teleport`: mouse-driven interface for selecting and teleporting units
+- `gui/biomes`: visualize and inspect biome regions on the map
 
 ## New Features
 - `uniform-unstick`: add overlay to the squad equipment screen to show a equipment conflict report and give you a one-click button to fix
diff --git a/docs/gui/biomes.rst b/docs/gui/biomes.rst
new file mode 100644
index 0000000000..550b0b30fa
--- /dev/null
+++ b/docs/gui/biomes.rst
@@ -0,0 +1,17 @@
+gui/biomes
+==========
+
+.. dfhack-tool::
+    :summary: Visualize and inspect biome regions on the map.
+    :tags: fort inspection map
+
+This script shows the boundaries of the biome regions on the map.
+Hover over a biome entry in the list to get detailed info about it.
+
+
+Usage
+-----
+
+::
+
+    gui/biomes
diff --git a/gui/biomes.lua b/gui/biomes.lua
new file mode 100644
index 0000000000..8627b7cc52
--- /dev/null
+++ b/gui/biomes.lua
@@ -0,0 +1,431 @@
+-- Visualize and inspect biome regions on the map.
+
+local RELOAD = false -- set to true when actively working on this script
+
+local gui = require('gui')
+local widgets = require('gui.widgets')
+local guidm = require('gui.dwarfmode')
+
+local INITIAL_LIST_HEIGHT = 5
+local INITIAL_INFO_HEIGHT = 15
+
+local texturesOnOff8x12 = dfhack.textures.loadTileset('hack/data/art/on-off.png', 8, 12, true)
+local LIST_ITEM_HIGHLIGHTED = dfhack.textures.getTexposByHandle(texturesOnOff8x12[1]) -- yellow-ish indicator
+
+local texturesOnOff = dfhack.textures.loadTileset('hack/data/art/on-off_top-left.png', 32, 32, true)
+local TILE_HIGHLIGHTED = dfhack.textures.getTexposByHandle(texturesOnOff[1]) -- yellow-ish indicator
+if TILE_HIGHLIGHTED < 0 then -- use a fallback
+    TILE_HIGHLIGHTED = 88 -- `X`
+end
+
+local texturesSmallLetters = dfhack.textures.loadTileset('hack/data/art/curses-small-letters_top-left.png', 32, 32, true)
+local TILE_STARTING_SYMBOL = dfhack.textures.getTexposByHandle(texturesSmallLetters[1])
+if TILE_STARTING_SYMBOL < 0 then -- use a fallback
+    TILE_STARTING_SYMBOL = 97 -- `a`
+end
+
+local biomeTypeNames = {
+    MOUNTAIN = "Mountain",
+    GLACIER = "Glacier",
+    TUNDRA = "Tundra",
+    SWAMP_TEMPERATE_FRESHWATER = "Temperate Freshwater Swamp",
+    SWAMP_TEMPERATE_SALTWATER = "Temperate Saltwater Swamp",
+    MARSH_TEMPERATE_FRESHWATER = "Temperate Freshwater Marsh",
+    MARSH_TEMPERATE_SALTWATER = "Temperate Saltwater Marsh",
+    SWAMP_TROPICAL_FRESHWATER = "Tropical Freshwater Swamp",
+    SWAMP_TROPICAL_SALTWATER = "Tropical Saltwater Swamp",
+    SWAMP_MANGROVE = "Mangrove Swamp",
+    MARSH_TROPICAL_FRESHWATER = "Tropical Freshwater Marsh",
+    MARSH_TROPICAL_SALTWATER = "Tropical Saltwater Marsh",
+    FOREST_TAIGA = "Taiga Forest",
+    FOREST_TEMPERATE_CONIFER = "Temperate Conifer Forest",
+    FOREST_TEMPERATE_BROADLEAF = "Temperate Broadleaf Forest",
+    FOREST_TROPICAL_CONIFER = "Tropical Conifer Forest",
+    FOREST_TROPICAL_DRY_BROADLEAF = "Tropical Dry Broadleaf Forest",
+    FOREST_TROPICAL_MOIST_BROADLEAF = "Tropical Moist Broadleaf Forest",
+    GRASSLAND_TEMPERATE = "Temperate Grassland",
+    SAVANNA_TEMPERATE = "Temperate Savanna",
+    SHRUBLAND_TEMPERATE = "Temperate Shrubland",
+    GRASSLAND_TROPICAL = "Tropical Grassland",
+    SAVANNA_TROPICAL = "Tropical Savanna",
+    SHRUBLAND_TROPICAL = "Tropical Shrubland",
+    DESERT_BADLAND = "Badland Desert",
+    DESERT_ROCK = "Rock Desert",
+    DESERT_SAND = "Sand Desert",
+    OCEAN_TROPICAL = "Tropical Ocean",
+    OCEAN_TEMPERATE = "Temperate Ocean",
+    OCEAN_ARCTIC = "Arctic Ocean",
+    POOL_TEMPERATE_FRESHWATER = "Temperate Freshwater Pool",
+    POOL_TEMPERATE_BRACKISHWATER = "Temperate Brackishwater Pool",
+    POOL_TEMPERATE_SALTWATER = "Temperate Saltwater Pool",
+    POOL_TROPICAL_FRESHWATER = "Tropical Freshwater Pool",
+    POOL_TROPICAL_BRACKISHWATER = "Tropical Brackishwater Pool",
+    POOL_TROPICAL_SALTWATER = "Tropical Saltwater Pool",
+    LAKE_TEMPERATE_FRESHWATER = "Temperate Freshwater Lake",
+    LAKE_TEMPERATE_BRACKISHWATER = "Temperate Brackishwater Lake",
+    LAKE_TEMPERATE_SALTWATER = "Temperate Saltwater Lake",
+    LAKE_TROPICAL_FRESHWATER = "Tropical Freshwater Lake",
+    LAKE_TROPICAL_BRACKISHWATER = "Tropical Brackishwater Lake",
+    LAKE_TROPICAL_SALTWATER = "Tropical Saltwater Lake",
+    RIVER_TEMPERATE_FRESHWATER = "Temperate Freshwater River",
+    RIVER_TEMPERATE_BRACKISHWATER = "Temperate Brackishwater River",
+    RIVER_TEMPERATE_SALTWATER = "Temperate Saltwater River",
+    RIVER_TROPICAL_FRESHWATER = "Tropical Freshwater River",
+    RIVER_TROPICAL_BRACKISHWATER = "Tropical Brackishwater River",
+    RIVER_TROPICAL_SALTWATER = "Tropical Saltwater River",
+    SUBTERRANEAN_WATER = "Subterranean Water",
+    SUBTERRANEAN_CHASM = "Subterranean Chasm",
+    SUBTERRANEAN_LAVA = "Subterranean Lava",
+}
+
+local function find(t, predicate)
+    for k, item in pairs(t) do
+        if predicate(k, item) then
+            return k, item
+        end
+    end
+    return nil
+end
+
+local regionBiomeMap = {}
+local biomesMap = {}
+local biomeList = {}
+local function gatherBiomeInfo(z)
+    local maxX, maxY, maxZ = dfhack.maps.getTileSize()
+    maxX = maxX - 1; maxY = maxY - 1; maxZ = maxZ - 1
+
+    z = z or df.global.window_z
+
+    --for z = 0, maxZ do
+    for y = 0, maxY do
+        for x = 0, maxX do
+            local rgnX, rgnY = dfhack.maps.getTileBiomeRgn(x,y,z)
+            if rgnX == nil then goto continue end
+
+            local regionBiomesX = regionBiomeMap[rgnX]
+            if not regionBiomesX then
+                regionBiomesX = {}
+                regionBiomeMap[rgnX] = regionBiomesX
+            end
+            local regionBiomesXY = regionBiomesX[rgnY]
+            if not regionBiomesXY then
+                regionBiomesXY = {
+                    biomeTypeId = dfhack.maps.getBiomeType(rgnX, rgnY),
+                    biome = dfhack.maps.getRegionBiome(rgnX, rgnY),
+                }
+                regionBiomesX[rgnY] = regionBiomesXY
+            end
+
+            local biomeTypeId = regionBiomesXY.biomeTypeId
+            local biome = regionBiomesXY.biome
+
+            local biomesZ = biomesMap[z]
+            if not biomesZ then
+                biomesZ = {}
+                biomesMap[z] = biomesZ
+            end
+            local biomesZY = biomesZ[y]
+            if not biomesZY then
+                biomesZY = {}
+                biomesZ[y] = biomesZY
+            end
+
+            local function currentBiome(_, item)
+                return item.biome == biome
+            end
+            local ix = find(biomeList, currentBiome)
+            if not ix then
+                local ch = string.char(string.byte('a') + #biomeList)
+                table.insert(biomeList, {biome = biome, char = ch, typeId = biomeTypeId})
+                ix = #biomeList
+            end
+
+            biomesZY[x] = ix
+
+            ::continue::
+        end
+    end
+    --end
+end
+
+-- always gather info at the very bottom first: this ensures the important biomes are
+-- always in the same order (high up in the air strange things happen)
+gatherBiomeInfo(0)
+
+--------------------------------------------------------------------------------
+
+local TITLE = "Biomes"
+
+if RELOAD then BiomeVisualizerLegend = nil end
+BiomeVisualizerLegend = defclass(BiomeVisualizerLegend, widgets.Window)
+BiomeVisualizerLegend.ATTRS {
+    frame_title=TITLE,
+    frame_inset=0,
+    resizable=true,
+    resize_min={h=5, w = 14},
+    frame = {
+        w = 47,
+        h = INITIAL_LIST_HEIGHT + 2 + INITIAL_INFO_HEIGHT,
+        -- just under the minimap:
+        r = 2,
+        t = 18,
+    },
+}
+
+local function GetBiomeName(biome, biomeTypeId)
+    -- based on probe.cpp
+    local sav = biome.savagery
+    local evi = biome.evilness;
+    local sindex = sav > 65 and 2 or sav < 33 and 0 or 1
+    local eindex = evi > 65 and 2 or evi < 33 and 0 or 1
+    local surr = sindex + eindex * 3 +1; --in Lua arrays are 1-based
+
+    local surroundings = {
+        "Serene", "Mirthful", "Joyous Wilds",
+        "Calm", "Wilderness", "Untamed Wilds",
+        "Sinister", "Haunted", "Terrifying"
+    }
+    local surrounding = surroundings[surr]
+
+    local name = biomeTypeNames[df.biome_type[biomeTypeId]] or "DFHACK_Unknown"
+
+    return ([[%s %s]]):format(surrounding, name)
+end
+
+function BiomeVisualizerLegend:init()
+    local list = widgets.List{
+        view_id = 'list',
+        frame = { t = 0, b = INITIAL_INFO_HEIGHT + 1 },
+        frame_inset = 0,
+        icon_width = 1,
+        text_pen = { fg = COLOR_GREY, bg = COLOR_BLACK }, -- this makes selection stand out more
+        on_select = self:callback('onSelectEntry'),
+    }
+    local tooltip_panel = widgets.Panel{
+        view_id='tooltip_panel',
+        autoarrange_subviews=true,
+        frame = { b = 0, h = INITIAL_INFO_HEIGHT },
+        frame_style=gui.INTERIOR_FRAME,
+        frame_background=gui.CLEAR_PEN,
+        subviews={
+            widgets.Label{
+                view_id='label',
+                text_to_wrap='',
+                scroll_keys={},
+            },
+        },
+    }
+    self:addviews{
+        list,
+        tooltip_panel,
+    }
+
+    self.list = list
+    self.tooltip_panel = tooltip_panel
+
+    self:UpdateChoices()
+end
+
+local PEN_ACTIVE_ICON = dfhack.pen.parse{tile=LIST_ITEM_HIGHLIGHTED}
+local PEN_NO_ICON = nil
+
+function BiomeVisualizerLegend:get_icon_pen_callback(ix)
+    return function ()
+        if self.SelectedIndex == ix then
+            return PEN_ACTIVE_ICON
+        else
+            return PEN_NO_ICON
+        end
+    end
+end
+
+function BiomeVisualizerLegend:get_text_pen_callback(ix)
+    return function ()
+        if self.MapHoverIndex == ix then
+            return self.SelectedIndex == ix
+                and { fg = COLOR_BLACK, bg = COLOR_LIGHTCYAN }
+                 or { fg = COLOR_BLACK, bg = COLOR_GREY }
+        else
+            return nil
+        end
+    end
+end
+
+function BiomeVisualizerLegend:onSelectEntry(idx, option)
+    self.SelectedIndex = idx
+    self.SelectedOption = option
+
+    self:ShowTooltip(option)
+end
+
+function BiomeVisualizerLegend:UpdateChoices()
+    local choices = self.list:getChoices() or {}
+    for i = #choices + 1, #biomeList do
+        local biomeExt = biomeList[i]
+        table.insert(choices, {
+            text = {{
+                pen = self:get_text_pen_callback(#choices+1),
+                text = ([[%s: %s]]):format(biomeExt.char, GetBiomeName(biomeExt.biome, biomeExt.typeId)),
+            }},
+            icon = self:get_icon_pen_callback(#choices+1),
+            biomeTypeId = biomeExt.typeId,
+            biome = biomeExt.biome,
+        })
+    end
+    self.list:setChoices(choices)
+end
+
+do -- implementation of onMouseHoverEntry(idx, option)
+    function BiomeVisualizerLegend:onRenderFrame(dc, rect)
+        BiomeVisualizerLegend.super.onRenderFrame(self, dc, rect)
+
+        local list = self.list
+        local currentHoverIx = list:getIdxUnderMouse()
+        local oldIx = self.HoverIndex
+        if currentHoverIx ~= oldIx then
+            self.HoverIndex = currentHoverIx
+            if self.onMouseHoverEntry then
+                local choices = list:getChoices()
+                self:onMouseHoverEntry(currentHoverIx, choices[currentHoverIx])
+            end
+        end
+    end
+end
+
+local function add_field_text(lines, biome, field_name)
+    lines[#lines+1] = ("%s: %s"):format(field_name, biome[field_name])
+    lines[#lines+1] = NEWLINE
+end
+
+local function get_tooltip_text(option)
+    if not option then
+        return ""
+    end
+
+    local text = {}
+    text[#text+1] = ("type: %s"):format(df.biome_type[option.biomeTypeId])
+    text[#text+1] = NEWLINE
+
+    local biome = option.biome
+
+    add_field_text(text, biome, "savagery")
+    add_field_text(text, biome, "evilness")
+    table.insert(text, NEWLINE)
+
+    add_field_text(text, biome, "elevation")
+    add_field_text(text, biome, "rainfall")
+    add_field_text(text, biome, "drainage")
+    add_field_text(text, biome, "vegetation")
+    add_field_text(text, biome, "temperature")
+    add_field_text(text, biome, "volcanism")
+    table.insert(text, NEWLINE)
+
+    local flags = biome.flags
+    if flags.is_lake then
+        text[#text+1] = "lake"
+        text[#text+1] = NEWLINE
+    end
+    if flags.is_brook then
+        text[#text+1] = "brook"
+        text[#text+1] = NEWLINE
+    end
+
+    return text
+end
+
+function BiomeVisualizerLegend:onMouseHoverEntry(idx, option)
+    self:ShowTooltip(option or self.SelectedOption)
+end
+
+function BiomeVisualizerLegend:ShowTooltip(option)
+    local text = get_tooltip_text(option)
+
+    local tooltip_panel = self.tooltip_panel
+    local lbl = tooltip_panel.subviews.label
+
+    lbl:setText(text)
+end
+
+function BiomeVisualizerLegend:onRenderBody(painter)
+    local thisPos = self:getMouseFramePos()
+    local pos = dfhack.gui.getMousePos()
+
+    if not thisPos and pos then
+        local N = safe_index(biomesMap, pos.z, pos.y, pos.x)
+        if N then
+            local choices = self.list:getChoices()
+            local option = choices[N]
+
+            self.MapHoverIndex = N
+            self:ShowTooltip(option)
+        end
+    else
+        self.MapHoverIndex = nil
+    end
+
+    BiomeVisualizerLegend.super.onRenderBody(self, painter)
+end
+
+--------------------------------------------------------------------------------
+
+if RELOAD then BiomeVisualizer = nil end
+BiomeVisualizer = defclass(BiomeVisualizer, gui.ZScreen)
+BiomeVisualizer.ATTRS{
+    focus_path='BiomeVisualizer',
+    pass_movement_keys=true,
+}
+
+function BiomeVisualizer:init()
+    local legend = BiomeVisualizerLegend{view_id = 'legend'}
+    self:addviews{legend}
+end
+
+function BiomeVisualizer:onRenderFrame(dc, rect)
+    BiomeVisualizer.super.onRenderFrame(self, dc, rect)
+
+    if not dfhack.screen.inGraphicsMode() and not gui.blink_visible(500) then
+        return
+    end
+
+    local z = df.global.window_z
+    if not biomesMap[z] then
+        gatherBiomeInfo(z)
+        self.subviews.legend:UpdateChoices()
+    end
+
+    local function get_overlay_pen(pos)
+        local self = self
+        local safe_index = safe_index
+        local biomes = biomesMap
+
+        local N = safe_index(biomes, pos.z, pos.y, pos.x)
+        if not N then return end
+
+        local idxSelected = self.subviews.legend.SelectedIndex
+        local idxTile = (N == idxSelected)
+                    and TILE_HIGHLIGHTED
+                    or TILE_STARTING_SYMBOL + (N-1)
+        local color = (N == idxSelected)
+                    and COLOR_CYAN
+                    or COLOR_GREY
+        local ch = string.char(string.byte('a') + (N-1))
+        return color, ch, idxTile
+    end
+
+    guidm.renderMapOverlay(get_overlay_pen, nil) -- nil for bounds means entire viewport
+end
+
+function BiomeVisualizer:onDismiss()
+    view = nil
+end
+
+if not dfhack.isMapLoaded() then
+    qerror('gui/biomes requires a map to be loaded')
+end
+
+if RELOAD and view then
+    view:dismiss()
+    -- view is nil now
+end
+
+view = view and view:raise() or BiomeVisualizer{}:show()