diff --git a/options/locale/locale_en-US.json b/options/locale/locale_en-US.json
index 1c332a8337..c3f2e899c2 100644
--- a/options/locale/locale_en-US.json
+++ b/options/locale/locale_en-US.json
@@ -1412,6 +1412,7 @@
   "repo.issues.new.open_projects": "Open Projects",
   "repo.issues.new.closed_projects": "Closed Projects",
   "repo.issues.new.no_items": "No items",
+  "repo.issues.custom_fields": "Custom Fields",
   "repo.issues.new.milestone": "Milestone",
   "repo.issues.new.no_milestone": "No Milestone",
   "repo.issues.new.clear_milestone": "Clear milestone",
diff --git a/routers/web/repo/issue_custom_field.go b/routers/web/repo/issue_custom_field.go
new file mode 100644
index 0000000000..d9345f9c65
--- /dev/null
+++ b/routers/web/repo/issue_custom_field.go
@@ -0,0 +1,33 @@
+// Copyright 2026 Moko Consulting <hello@mokoconsulting.tech>
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package repo
+
+import (
+	"fmt"
+	"net/http"
+
+	issues_model "code.mokoconsulting.tech/MokoConsulting/MokoGitea/models/issues"
+	"code.mokoconsulting.tech/MokoConsulting/MokoGitea/services/context"
+)
+
+// UpdateIssueCustomField handles POST to set a custom field value on an issue.
+func UpdateIssueCustomField(ctx *context.Context) {
+	issueID := ctx.PathParamInt64("id")
+	fieldID := ctx.PathParamInt64("field_id")
+	value := ctx.FormString("value")
+
+	// Look up issue to get the index for redirect.
+	issue, err := issues_model.GetIssueByID(ctx, issueID)
+	if err != nil {
+		ctx.ServerError("GetIssueByID", err)
+		return
+	}
+
+	if err := issues_model.SetCustomFieldValue(ctx, issueID, fieldID, value); err != nil {
+		ctx.ServerError("SetCustomFieldValue", err)
+		return
+	}
+
+	ctx.Redirect(fmt.Sprintf("%s/issues/%d", ctx.Repo.RepoLink, issue.Index), http.StatusSeeOther)
+}
diff --git a/routers/web/repo/issue_view.go b/routers/web/repo/issue_view.go
index 7ab1be62f0..dfa2a8b34e 100644
--- a/routers/web/repo/issue_view.go
+++ b/routers/web/repo/issue_view.go
@@ -4,6 +4,7 @@
 package repo
 
 import (
+	"encoding/json"
 	"fmt"
 	"math/big"
 	"net/http"
@@ -337,6 +338,25 @@ func ViewIssue(ctx *context.Context) {
 
 	ctx.Data["IsProjectsEnabled"] = ctx.Repo.Permission.CanRead(unit.TypeProjects)
 	ctx.Data["IsAttachmentEnabled"] = setting.Attachment.Enabled
+
+	// Load custom fields for the issue sidebar.
+	customFieldDefs, _ := issues_model.GetCustomFieldsByRepo(ctx, ctx.Repo.Repository.ID)
+	ctx.Data["CustomFieldDefs"] = customFieldDefs
+	customFieldValues := make(map[int64]string)
+	fieldOptions := make(map[int64][]string)
+	if len(customFieldDefs) > 0 {
+		customFieldValues, _ = issues_model.GetCustomFieldValuesMap(ctx, issue.ID)
+		for _, f := range customFieldDefs {
+			if f.Options != "" {
+				var opts []string
+				if err := json.Unmarshal([]byte(f.Options), &opts); err == nil {
+					fieldOptions[f.ID] = opts
+				}
+			}
+		}
+	}
+	ctx.Data["CustomFieldValues"] = customFieldValues
+	ctx.Data["CustomFieldOptions"] = fieldOptions
 	upload.AddUploadContext(ctx, "comment")
 
 	if err := issue.LoadAttributes(ctx); err != nil {
diff --git a/routers/web/web.go b/routers/web/web.go
index 4a8ecc18ae..745d4d34e0 100644
--- a/routers/web/web.go
+++ b/routers/web/web.go
@@ -1397,6 +1397,7 @@ func registerWebRoutes(m *web.Router, webAuth *AuthMiddleware) {
 			m.Post("/projects/column", reqRepoIssuesOrPullsWriter, reqRepoProjectsWriter, repo.UpdateIssueProjectColumn)
 			m.Post("/assignee", reqRepoIssuesOrPullsWriter, repo.UpdateIssueAssignee)
 			m.Post("/status", reqRepoIssuesOrPullsWriter, repo.UpdateIssueStatus)
+			m.Post("/{id}/custom-fields/{field_id}", reqRepoIssuesOrPullsWriter, repo.UpdateIssueCustomField)
 			m.Post("/delete", reqRepoAdmin, repo.BatchDeleteIssues)
 			m.Delete("/unpin/{index}", reqRepoAdmin, repo.IssueUnpin)
 			m.Post("/move_pin", reqRepoAdmin, repo.IssuePinMove)
diff --git a/templates/repo/issue/sidebar/custom_fields.tmpl b/templates/repo/issue/sidebar/custom_fields.tmpl
new file mode 100644
index 0000000000..99757434c4
--- /dev/null
+++ b/templates/repo/issue/sidebar/custom_fields.tmpl
@@ -0,0 +1,33 @@
+{{if .CustomFieldDefs}}
+<div class="divider"></div>
+<div class="tw-flex tw-flex-col tw-gap-2">
+	{{$issueID := .Issue.ID}}
+	{{$repoLink := .RepoLink}}
+	{{$canModify := .HasIssuesOrPullsWritePermission}}
+	{{$values := .CustomFieldValues}}
+	{{$fieldOptions := .CustomFieldOptions}}
+	{{range .CustomFieldDefs}}
+		{{$currentVal := index $values .ID}}
+		<div class="tw-flex tw-items-center tw-justify-between tw-gap-2">
+			<span class="text grey tw-text-sm" {{if .Description}}title="{{.Description}}"{{end}}>{{.Name}}</span>
+			{{if and $canModify (eq .Options "")}}
+				{{/* Non-dropdown: just display the value */}}
+				<span class="tw-text-sm">{{if $currentVal}}{{$currentVal}}{{else}}<span class="text grey">—</span>{{end}}</span>
+			{{else if $canModify}}
+				<form method="post" action="{{$repoLink}}/issues/{{$issueID}}/custom-fields/{{.ID}}" class="tw-inline">
+					{{$.CsrfTokenHtml}}
+					<select name="value" class="ui compact mini dropdown tw-max-w-48" onchange="this.form.submit()">
+						<option value="">—</option>
+						{{$opts := index $fieldOptions .ID}}
+						{{range $opts}}
+							<option value="{{.}}" {{if eq . $currentVal}}selected{{end}}>{{.}}</option>
+						{{end}}
+					</select>
+				</form>
+			{{else}}
+				<span class="tw-text-sm">{{if $currentVal}}{{$currentVal}}{{else}}<span class="text grey">—</span>{{end}}</span>
+			{{end}}
+		</div>
+	{{end}}
+</div>
+{{end}}
diff --git a/templates/repo/issue/view_content/sidebar.tmpl b/templates/repo/issue/view_content/sidebar.tmpl
index 6427d10968..9f064ce6ee 100644
--- a/templates/repo/issue/view_content/sidebar.tmpl
+++ b/templates/repo/issue/view_content/sidebar.tmpl
@@ -7,6 +7,8 @@
 
 	{{template "repo/issue/sidebar/label_list" $.IssuePageMetaData}}
 
+	{{template "repo/issue/sidebar/custom_fields" $}}
+
 	{{template "repo/issue/sidebar/milestone_list" $.IssuePageMetaData}}
 	{{if .IsProjectsEnabled}}
 		{{template "repo/issue/sidebar/project_list" $.IssuePageMetaData}}