diff --git a/R/geom-.r b/R/geom-.r
index 92e2b8a3b..65075bf4b 100644
--- a/R/geom-.r
+++ b/R/geom-.r
@@ -580,6 +580,10 @@ Geom <- gganimintproto("Geom",
     if("group" %in% names(g$aes) && g$geom %in% data.object.geoms){
       g$nest_order <- c(g$nest_order, "group")
     }
+    ## If subgroup is specified for polygon, flag it for JS renderer.
+    if("subgroup" %in% names(g$aes) && g$geom == "polygon"){
+      g$data_has_subgroup <- TRUE
+    }
     ## If user did not specify aes(group), then use group=1.
     if(! "group" %in% names(g$aes)){
       g.data$group <- 1
diff --git a/R/geom-polygon.r b/R/geom-polygon.r
index 4fec1868e..4bcf0b337 100644
--- a/R/geom-polygon.r
+++ b/R/geom-polygon.r
@@ -101,7 +101,7 @@ GeomPolygon <- gganimintproto("GeomPolygon", Geom,
   },
 
   default_aes = aes(colour = "NA", fill = "grey20", size = 0.5, linetype = 1,
-    alpha = NA),
+    alpha = NA, subgroup = NULL),
 
   handle_na = function(data, params) {
     data
diff --git a/inst/htmljs/animint.js b/inst/htmljs/animint.js
index bfcc4b07f..03f239dea 100644
--- a/inst/htmljs/animint.js
+++ b/inst/htmljs/animint.js
@@ -1370,11 +1370,34 @@ var animint = function (to_select, json_file) {
         fill = "none";
         fill_off = "none";
       }
+      // Create d3.geo.path with null projection once (no geographic
+      // reprojection; coordinates are already in pixel space after
+      // applying scales). Only needed for polygon subgroup holes.
+      var geoPath = g_info.data_has_subgroup ? d3.geo.path().projection(null) : null;
       data_to_bind = kv;
       eActions = function (e) {
         e.attr("d", function (d) {
-          return lineThing(keyed_data[d.value]);
-        })
+          var group_data = keyed_data[d.value];
+          if(g_info.data_has_subgroup){
+            // Build a GeoJSON Polygon: first ring is exterior,
+            // subsequent rings are holes (as per GeoJSON spec).
+            var by_subgroup = d3.nest()
+              .key(function(r){ return r["subgroup"]; })
+              .entries(group_data);
+            var rings = by_subgroup.map(function(sg){
+              var coords = sg.values.map(function(pt){
+                return [scales.x(pt.x), scales.y(pt.y)];
+              });
+              coords.push(coords[0].slice()); // close ring
+              return coords;
+            });
+            return geoPath({ type: "Polygon", coordinates: rings });
+          }
+          return lineThing(group_data);
+        });
+        if(g_info.data_has_subgroup){
+          e.style("fill-rule", "evenodd");
+        }
       };
       eAppend = "path";
     }else{
diff --git a/tests/testthat/test-renderer-polygon-subgroup.R b/tests/testthat/test-renderer-polygon-subgroup.R
new file mode 100644
index 000000000..246aaef6b
--- /dev/null
+++ b/tests/testthat/test-renderer-polygon-subgroup.R
@@ -0,0 +1,160 @@
+acontext("polygon subgroup holes")
+library(animint2)
+library(isoband)
+library(data.table)
+library(jsonlite)
+
+make_viz <- function(m, subgroup = TRUE) {
+  res <- as.data.table(
+    isoband::isobands(
+      (1:ncol(m)) / (ncol(m) + 1),
+      (nrow(m):1) / (nrow(m) + 1),
+      m, 0.5, 1.5
+    )[[1]]
+  )
+  if (subgroup) {
+    list(poly = ggplot() +
+      geom_polygon(aes(x, y, group = 1, subgroup = id), data = res))
+  } else {
+    list(poly = ggplot() +
+      geom_polygon(aes(x, y, group = id), data = res))
+  }
+}
+
+compile <- function(viz) {
+  out_dir <- tempfile()
+  animint2dir(viz, out.dir = out_dir, open.browser = FALSE)
+  list(
+    json = jsonlite::fromJSON(file.path(out_dir, "plot.json")),
+    tsv  = read.table(
+      file.path(out_dir, "geom1_polygon_poly_chunk1.tsv"),
+      header = TRUE, sep = "\t"
+    ),
+    dir = out_dir
+  )
+}
+
+m_simple <- matrix(
+  c(0, 0, 0, 0, 0, 0,
+    0, 1, 1, 1, 1, 0,
+    0, 1, 0, 0, 1, 0,
+    0, 1, 0, 0, 1, 0,
+    0, 1, 1, 1, 1, 0,
+    0, 0, 0, 0, 0, 0),
+  6, 6, byrow = TRUE)
+
+m_no_hole <- rbind(
+  c(0, 0, 0, 0, 0, 0, 0),
+  c(0, 1, 1, 1, 1, 1, 0),
+  c(0, 1, 1, 1, 1, 1, 0),
+  c(0, 1, 1, 1, 1, 1, 0),
+  c(0, 1, 1, 1, 1, 1, 0),
+  c(0, 1, 1, 1, 1, 1, 0),
+  c(0, 0, 0, 0, 0, 0, 0))
+
+m_hole_and_mid <- rbind(
+  c(0, 0, 0, 0, 0, 0, 0),
+  c(0, 1, 1, 1, 1, 1, 0),
+  c(0, 1, 0, 0, 0, 1, 0),
+  c(0, 1, 0, 1, 0, 1, 0),
+  c(0, 1, 0, 0, 0, 1, 0),
+  c(0, 1, 1, 1, 1, 1, 0),
+  c(0, 0, 0, 0, 0, 0, 0))
+
+## --- compiler tests (no browser needed) ---
+
+test_that("subgroup flag and TSV column present when subgroup used", {
+  out <- compile(make_viz(m_simple, subgroup = TRUE))
+  expect_true(out$json$geoms$geom1_polygon_poly$data_has_subgroup)
+  expect_true("subgroup" %in% names(out$tsv))
+  expect_equal(length(unique(out$tsv$subgroup)), 2)
+})
+
+test_that("subgroup flag absent when subgroup not used", {
+  out <- compile(make_viz(m_simple, subgroup = FALSE))
+  expect_false(isTRUE(out$json$geoms$geom1_polygon_poly$data_has_subgroup))
+})
+
+test_that("no_hole case has 1 subgroup, hole_and_mid has 3", {
+  out_no <- compile(make_viz(m_no_hole, subgroup = TRUE))
+  expect_equal(length(unique(out_no$tsv$subgroup)), 1)
+  out_mid <- compile(make_viz(m_hole_and_mid, subgroup = TRUE))
+  expect_equal(length(unique(out_mid$tsv$subgroup)), 3)
+})
+
+test_that("multiple groups with subgroup both appear in TSV", {
+  res1 <- as.data.table(isoband::isobands(
+    (1:ncol(m_simple)) / (ncol(m_simple) + 1),
+    (nrow(m_simple):1) / (nrow(m_simple) + 1),
+    m_simple, 0.5, 1.5)[[1]])[, grp := "A"]
+  res2 <- as.data.table(isoband::isobands(
+    (1:ncol(m_no_hole)) / (ncol(m_no_hole) + 1),
+    (nrow(m_no_hole):1) / (nrow(m_no_hole) + 1),
+    m_no_hole, 0.5, 1.5)[[1]])[, grp := "B"]
+  combined <- rbind(res1, res2)
+  viz_multi <- list(
+    poly = ggplot() +
+      geom_polygon(aes(x, y, group = grp, subgroup = id), data = combined)
+  )
+  out_dir <- tempfile()
+  animint2dir(viz_multi, out.dir = out_dir, open.browser = FALSE)
+  tsv <- read.table(
+    file.path(out_dir, "geom1_polygon_poly_chunk1.tsv"),
+    header = TRUE, sep = "\t"
+  )
+  expect_true("subgroup" %in% names(tsv))
+  expect_equal(length(unique(tsv$group)), 2)
+})
+
+## --- renderer tests (browser required) ---
+
+res_A <- as.data.table(isoband::isobands(
+  (1:ncol(m_simple)) / (ncol(m_simple) + 1),
+  (nrow(m_simple):1) / (nrow(m_simple) + 1),
+  m_simple, 0.5, 1.5)[[1]])[, grp := "A"]
+res_B <- as.data.table(isoband::isobands(
+  (1:ncol(m_no_hole)) / (ncol(m_no_hole) + 1),
+  (nrow(m_no_hole):1) / (nrow(m_no_hole) + 1),
+  m_no_hole, 0.5, 1.5)[[1]])[, grp := "B"]
+res_click <- rbind(res_A, res_B)
+
+viz_click <- list(
+  poly = ggplot() +
+    geom_polygon(
+      aes(x, y, group = grp, subgroup = id, fill = grp,
+          id = paste0("poly_", grp)),
+      clickSelects = "grp",
+      data = res_click
+    )
+)
+
+info <- animint2HTML(viz_click)
+
+test_that("one path per group with evenodd fill-rule and multiple subpaths", {
+  html <- getHTML()
+  path_nodes <- getNodeSet(html, "//path[@class='geom']")
+  ## 2 groups A and B => 2 path elements (not 4)
+  expect_equal(length(path_nodes), 2)
+  ## fill-rule must be evenodd
+  styles <- sapply(path_nodes, xmlGetAttr, "style")
+  expect_true(any(grepl("evenodd", styles)))
+  ## group A (with hole) must have multiple closed subpaths (M commands)
+  d_vals <- sapply(path_nodes, xmlGetAttr, "d")
+  m_counts <- sapply(d_vals, function(d) length(gregexpr("M", d)[[1]]))
+  expect_true(any(m_counts >= 2))
+})
+
+test_that("clickSelects works with subgroup polygons", {
+  ## click group A to deselect
+  clickID("poly_A")
+  Sys.sleep(1)
+  html_after <- getHTML()
+  path_nodes <- getNodeSet(html_after, "//path[@class='geom']")
+  expect_gt(length(path_nodes), 0)
+  ## click again to reselect
+  clickID("poly_A")
+  Sys.sleep(1)
+  html_restored <- getHTML()
+  path_nodes_restored <- getNodeSet(html_restored, "//path[@class='geom']")
+  expect_gte(length(path_nodes_restored), 1)
+})
\ No newline at end of file