diff --git a/finnow-api/source/profile/data_impl_sqlite.d b/finnow-api/source/profile/data_impl_sqlite.d
index 9eb0405..5fe6550 100644
--- a/finnow-api/source/profile/data_impl_sqlite.d
+++ b/finnow-api/source/profile/data_impl_sqlite.d
@@ -152,6 +152,7 @@ class SqliteProfileDataSource : ProfileDataSource {
         import std.file : exists;
         bool needsInit = !exists(path);
         this.db = Database(path);
+        db.run("PRAGMA foreign_keys = ON");
         if (needsInit) {
             infoF!"Initializing database: %s"(dbPath);
             db.run(SCHEMA);
diff --git a/finnow-api/source/transaction/service.d b/finnow-api/source/transaction/service.d
index 975dcb2..d69157b 100644
--- a/finnow-api/source/transaction/service.d
+++ b/finnow-api/source/transaction/service.d
@@ -286,6 +286,11 @@ TransactionCategoryResponse createCategory(ProfileDataSource ds, in CategoryPayl
     if (!payload.parentId.isNull && !repo.existsById(payload.parentId.get)) {
         throw new HttpStatusException(HttpStatus.BAD_REQUEST, "Invalid parent id.");
     }
+    import std.regex;
+    const colorHexRegex = ctRegex!`^(([0-9a-fA-F]{2}){3}|([0-9a-fA-F]){3})$`;
+    if (payload.color is null || matchFirst(payload.color, colorHexRegex).empty) {
+        throw new HttpStatusException(HttpStatus.BAD_REQUEST, "Invalid color hex string.");
+    }
     auto category = repo.insert(
         toOptional(payload.parentId),
         payload.name,
diff --git a/finnow-api/sql/schema.sql b/finnow-api/sql/schema.sql
index 2c8dbe6..3846c8a 100644
--- a/finnow-api/sql/schema.sql
+++ b/finnow-api/sql/schema.sql
@@ -110,7 +110,7 @@ CREATE TABLE transaction_line_item (
             ON UPDATE CASCADE ON DELETE CASCADE,
     CONSTRAINT fk_transaction_line_item_category
         FOREIGN KEY (category_id) REFERENCES transaction_category(id)
-            ON UPDATE CASCADE ON DELETE CASCADE
+            ON UPDATE CASCADE ON DELETE SET NULL
 );
 
 CREATE TABLE account_journal_entry (
diff --git a/web-app/src/api/transaction.ts b/web-app/src/api/transaction.ts
index 9234bda..07a8ad2 100644
--- a/web-app/src/api/transaction.ts
+++ b/web-app/src/api/transaction.ts
@@ -1,7 +1,7 @@
+import { useProfileStore } from '@/stores/profile-store'
 import { ApiClient } from './base'
 import type { Currency } from './data'
 import { type Page, type PageRequest } from './pagination'
-import type { Profile } from './profile'
 
 export interface TransactionVendor {
   id: number
@@ -134,9 +134,11 @@ export interface CreateCategoryPayload {
 export class TransactionApiClient extends ApiClient {
   readonly path: string
 
-  constructor(profile: Profile) {
+  constructor() {
     super()
-    this.path = `/profiles/${profile.name}`
+    const profileStore = useProfileStore()
+    if (!profileStore.state) throw new Error('No profile state!')
+    this.path = `/profiles/${profileStore.state.name}`
   }
 
   getVendors(): Promise<TransactionVendor[]> {
@@ -172,7 +174,7 @@ export class TransactionApiClient extends ApiClient {
   }
 
   updateCategory(id: number, data: CreateCategoryPayload): Promise<TransactionCategory> {
-    return super.postJson(this.path + '/categories/' + id, data)
+    return super.putJson(this.path + '/categories/' + id, data)
   }
 
   deleteCategory(id: number): Promise<void> {
diff --git a/web-app/src/components/CategoryDisplayItem.vue b/web-app/src/components/CategoryDisplayItem.vue
new file mode 100644
index 0000000..92238cd
--- /dev/null
+++ b/web-app/src/components/CategoryDisplayItem.vue
@@ -0,0 +1,78 @@
+<script setup lang="ts">
+import type { TransactionCategoryTree } from '@/api/transaction';
+import AppButton from './AppButton.vue';
+import { computed, ref } from 'vue';
+
+const props = defineProps<{
+  category: TransactionCategoryTree
+  editable: boolean
+}>()
+defineEmits<{
+  'edited': [number]
+  'deleted': [number]
+}>()
+const expanded = ref(false)
+const canExpand = computed(() => props.category.children.length > 0)
+</script>
+<template>
+  <div class="category-display-item" :class="{
+    'category-display-item-bg-1': category.depth % 2 === 0,
+    'category-display-item-bg-2': category.depth % 2 === 1
+  }">
+    <div class="category-display-item-content">
+      <div>
+        <h4 class="category-display-item-title">{{ category.name }}</h4>
+        <p class="category-display-item-description">{{ category.description }}</p>
+      </div>
+      <div class="category-display-item-color-indicator" :style="{ 'background-color': '#' + category.color }"></div>
+    </div>
+    <div v-if="editable" style="text-align: right;">
+      <AppButton icon="chevron-down" v-if="canExpand && !expanded" @click="expanded = true" />
+      <AppButton icon="chevron-up" v-if="canExpand && expanded" @click="expanded = false" />
+      <AppButton icon="wrench" @click="$emit('edited', category.id)" />
+      <AppButton icon="trash" @click="$emit('deleted', category.id)" />
+    </div>
+    <!-- Nested display item for each child: -->
+    <div style="margin-left: 1rem;" v-if="canExpand && expanded">
+      <CategoryDisplayItem v-for="child in category.children" :key="child.id" :category="child" :editable="editable"
+        @edited="c => $emit('edited', c)" @deleted="c => $emit('deleted', c)" />
+    </div>
+  </div>
+</template>
+<style lang="css">
+.category-display-item {
+  padding: 0.5rem 1rem;
+  margin: 1rem 0;
+  border-radius: 1rem;
+}
+
+.category-display-item-content {
+  display: flex;
+  justify-content: space-between;
+}
+
+.category-display-item-title {
+  margin: 0;
+}
+
+.category-display-item-description {
+  margin-top: 0.25rem;
+  margin-bottom: 0;
+  font-size: 14px;
+}
+
+.category-display-item-color-indicator {
+  width: 30px;
+  height: 30px;
+  border-radius: 50%;
+  border: 0.25rem solid black;
+}
+
+.category-display-item-bg-1 {
+  background-color: var(--bg-primary);
+}
+
+.category-display-item-bg-2 {
+  background-color: var(--bg-secondary);
+}
+</style>
diff --git a/web-app/src/components/EditCategoryModal.vue b/web-app/src/components/EditCategoryModal.vue
new file mode 100644
index 0000000..fc75d3d
--- /dev/null
+++ b/web-app/src/components/EditCategoryModal.vue
@@ -0,0 +1,96 @@
+<script setup lang="ts">
+import { TransactionApiClient, type TransactionCategory } from '@/api/transaction';
+import ModalWrapper from './ModalWrapper.vue';
+import { ref, useTemplateRef, type Ref } from 'vue';
+import AppForm from './form/AppForm.vue';
+import FormGroup from './form/FormGroup.vue';
+import FormControl from './form/FormControl.vue';
+import AppButton from './AppButton.vue';
+
+const props = defineProps<{
+  category?: TransactionCategory
+}>()
+const emit = defineEmits<{ saved: [TransactionCategory] }>()
+const modal = useTemplateRef('modal')
+
+// Form data:
+const name = ref('')
+const description = ref('')
+const color = ref('ffffff')
+const parentId: Ref<number | null> = ref(null)
+
+function show(): Promise<string | undefined> {
+  if (!modal.value) return Promise.resolve(undefined)
+  name.value = props.category?.name ?? ''
+  description.value = props.category?.description ?? ''
+  if (props.category) {
+    color.value = '#' + props.category.color
+  } else {
+    color.value = '#ffffff'
+  }
+  parentId.value = props.category?.parentId ?? null
+  return modal.value.show()
+}
+
+function canSave() {
+  const inputValid = name.value.trim().length > 0 &&
+    color.value.match('^#(([0-9a-fA-F]{2}){3}|([0-9a-fA-F]){3})$')
+  if (!inputValid) return false
+  if (props.category) {
+    return props.category.name.trim() !== name.value.trim() ||
+      props.category.description.trim() !== description.value.trim() ||
+      props.category.color.trim().toLowerCase() !== color.value.trim().toLowerCase() ||
+      props.category.parentId !== parentId.value
+  }
+  return true
+}
+
+async function doSave() {
+  const api = new TransactionApiClient()
+  const payload = {
+    name: name.value.trim(),
+    description: description.value.trim(),
+    color: color.value.trim().substring(1),
+    parentId: parentId.value
+  }
+  try {
+    let savedCategory = null
+    if (props.category) {
+      savedCategory = await api.updateCategory(props.category.id, payload)
+    } else {
+      savedCategory = await api.createCategory(payload)
+    }
+    emit('saved', savedCategory)
+    modal.value?.close('saved')
+  } catch (err) {
+    console.error(err)
+    modal.value?.close()
+  }
+}
+
+defineExpose({ show })
+</script>
+<template>
+  <ModalWrapper ref="modal">
+    <template v-slot:default>
+      <h2>{{ category ? 'Edit' : 'Add' }} Category</h2>
+      <AppForm>
+        <FormGroup>
+          <FormControl label="Name">
+            <input type="text" v-model="name" />
+          </FormControl>
+          <FormControl label="Color">
+            <input type="color" v-model="color" />
+          </FormControl>
+          <FormControl label="Description" style="min-width: 300px;">
+            <textarea v-model="description"></textarea>
+          </FormControl>
+        </FormGroup>
+      </AppForm>
+    </template>
+    <template v-slot:buttons>
+      <AppButton :disabled="!canSave()" @click="doSave()">Save</AppButton>
+      <AppButton button-style="secondary" @click="modal?.close()">Cancel</AppButton>
+    </template>
+  </ModalWrapper>
+</template>
diff --git a/web-app/src/components/EditVendorModal.vue b/web-app/src/components/EditVendorModal.vue
index 8efa78b..22a669d 100644
--- a/web-app/src/components/EditVendorModal.vue
+++ b/web-app/src/components/EditVendorModal.vue
@@ -5,14 +5,12 @@ import FormControl from './form/FormControl.vue';
 import FormGroup from './form/FormGroup.vue';
 import ModalWrapper from './ModalWrapper.vue';
 import { TransactionApiClient, type TransactionVendor } from '@/api/transaction';
-import { useProfileStore } from '@/stores/profile-store';
 import AppButton from './AppButton.vue';
 
 const props = defineProps<{
   vendor?: TransactionVendor
 }>()
 const emit = defineEmits<{ saved: [TransactionVendor] }>()
-const profileStore = useProfileStore()
 const modal = useTemplateRef('modal')
 
 // Form data:
@@ -23,7 +21,7 @@ function show(): Promise<string | undefined> {
   if (!modal.value) return Promise.resolve(undefined)
   name.value = props.vendor?.name ?? ''
   description.value = props.vendor?.description ?? ''
-  return modal.value?.show()
+  return modal.value.show()
 }
 
 function canSave() {
@@ -37,8 +35,7 @@ function canSave() {
 }
 
 async function doSave() {
-  if (!profileStore.state) return
-  const api = new TransactionApiClient(profileStore.state)
+  const api = new TransactionApiClient()
   const payload = {
     name: name.value.trim(),
     description: description.value.trim()
@@ -63,7 +60,7 @@ defineExpose({ show })
 <template>
   <ModalWrapper ref="modal">
     <template v-slot:default>
-      <h2>Add Vendor</h2>
+      <h2>{{ vendor ? 'Edit' : 'Add' }} Vendor</h2>
       <AppForm>
         <FormGroup>
           <FormControl label="Name">
@@ -73,7 +70,6 @@ defineExpose({ show })
             <textarea v-model="description"></textarea>
           </FormControl>
         </FormGroup>
-
       </AppForm>
     </template>
     <template v-slot:buttons>
diff --git a/web-app/src/pages/CategoriesPage.vue b/web-app/src/pages/CategoriesPage.vue
new file mode 100644
index 0000000..4f16aa2
--- /dev/null
+++ b/web-app/src/pages/CategoriesPage.vue
@@ -0,0 +1,80 @@
+<script setup lang="ts">
+import { TransactionApiClient, type TransactionCategory, type TransactionCategoryTree } from '@/api/transaction';
+import AppButton from '@/components/AppButton.vue';
+import AppPage from '@/components/AppPage.vue';
+import CategoryDisplayItem from '@/components/CategoryDisplayItem.vue';
+import EditCategoryModal from '@/components/EditCategoryModal.vue';
+import { showConfirm } from '@/util/alert';
+import { hideLoader, showLoader } from '@/util/loader';
+import { nextTick, onMounted, ref, useTemplateRef, type Ref } from 'vue';
+
+const editCategoryModal = useTemplateRef('editCategoryModal')
+
+const categories: Ref<TransactionCategoryTree[]> = ref([])
+const editedCategory: Ref<TransactionCategory | undefined> = ref(undefined)
+
+onMounted(async () => {
+  await loadCategories()
+})
+
+async function loadCategories() {
+  const api = new TransactionApiClient()
+  categories.value = await api.getCategories()
+}
+
+async function editCategory(categoryId: number) {
+  try {
+    const api = new TransactionApiClient()
+    editedCategory.value = await api.getCategory(categoryId)
+    await nextTick()
+    const result = await editCategoryModal.value?.show()
+    if (result === 'saved') {
+      await loadCategories()
+    }
+  } catch (err) {
+    console.error(err)
+  }
+}
+
+async function deleteCategory(categoryId: number) {
+  const result = await showConfirm('Are you sure you want to delete this category? It will be removed from all transactions. All sub-categories will also be removed.')
+  if (result) {
+    try {
+      showLoader()
+      const api = new TransactionApiClient()
+      await api.deleteCategory(categoryId)
+      await loadCategories()
+    } catch (err) {
+      console.error(err)
+    } finally {
+      hideLoader()
+    }
+  }
+}
+
+async function addCategory() {
+  editedCategory.value = undefined
+  const result = await editCategoryModal.value?.show()
+  if (result === 'saved') {
+    await loadCategories()
+  }
+}
+</script>
+<template>
+  <AppPage title="Categories">
+    <p>
+      Categories are used to group related transactions for your own organization,
+      as well as analytics. Categories are structured hierarchically, where each
+      category could have zero or more sub-categories.
+    </p>
+    <div>
+      <CategoryDisplayItem v-for="category in categories" :key="category.id" :category="category" :editable="true"
+        @edited="editCategory" @deleted="deleteCategory" />
+    </div>
+    <div style="text-align: right;">
+      <AppButton icon="plus" @click="addCategory()">Add Category</AppButton>
+    </div>
+
+    <EditCategoryModal ref="editCategoryModal" :category="editedCategory" />
+  </AppPage>
+</template>
diff --git a/web-app/src/pages/VendorsPage.vue b/web-app/src/pages/VendorsPage.vue
index 595d2d5..ebe52fb 100644
--- a/web-app/src/pages/VendorsPage.vue
+++ b/web-app/src/pages/VendorsPage.vue
@@ -3,11 +3,9 @@ import { TransactionApiClient, type TransactionVendor } from '@/api/transaction'
 import AppButton from '@/components/AppButton.vue';
 import AppPage from '@/components/AppPage.vue';
 import EditVendorModal from '@/components/EditVendorModal.vue';
-import { useProfileStore } from '@/stores/profile-store';
 import { showConfirm } from '@/util/alert';
 import { onMounted, ref, useTemplateRef, type Ref } from 'vue';
 
-const profileStore = useProfileStore()
 const vendors: Ref<TransactionVendor[]> = ref([])
 const editVendorModal = useTemplateRef('editVendorModal')
 const editedVendor: Ref<TransactionVendor | undefined> = ref()
@@ -17,8 +15,7 @@ onMounted(async () => {
 })
 
 async function loadVendors() {
-  if (!profileStore.state) return
-  const api = new TransactionApiClient(profileStore.state)
+  const api = new TransactionApiClient()
   vendors.value = await api.getVendors()
 }
 
@@ -39,10 +36,9 @@ async function editVendor(vendor: TransactionVendor) {
 }
 
 async function deleteVendor(vendor: TransactionVendor) {
-  if (!profileStore.state) return
   const confirmed = await showConfirm('Are you sure you want to delete this vendor? It will be permanently removed from all associated transactions.')
   if (!confirmed) return
-  const api = new TransactionApiClient(profileStore.state)
+  const api = new TransactionApiClient()
   await api.deleteVendor(vendor.id)
   await loadVendors()
 }
diff --git a/web-app/src/router/index.ts b/web-app/src/router/index.ts
index 5caf598..33a406d 100644
--- a/web-app/src/router/index.ts
+++ b/web-app/src/router/index.ts
@@ -73,6 +73,11 @@ const router = createRouter({
               component: () => import('@/pages/VendorsPage.vue'),
               meta: { title: 'Vendors' },
             },
+            {
+              path: 'categories',
+              component: () => import('@/pages/CategoriesPage.vue'),
+              meta: { title: 'Categories' },
+            },
           ],
         },
       ],