diff --git a/docs/RESPONSIVE_CSS.md b/docs/RESPONSIVE_CSS.md
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@@ -4,6 +4,115 @@
 
 Added responsive CSS to the Tablet Management System to improve mobile accessibility for internal technical staff. This addresses the issue where the interface was too wide for mobile devices.
 
+## ⚠️ TOP PRIORITY: Spanish Translation Required
+
+**Status:** Not started - Documentation only
+**Priority:** HIGH
+**Timeline:** To be determined
+
+The entire user interface needs to be translated from English to Spanish. This includes:
+
+### Scope of Translation
+- ✅ All template text (buttons, labels, headers, messages)
+- ✅ Navigation links
+- ✅ Form field labels and placeholders
+- ✅ Button text
+- ✅ Flash messages (success/error)
+- ✅ Table headers
+- ✅ Help text and descriptions
+- ✅ Page titles
+
+### Files to Translate
+| File | Status | Notes |
+|------|--------|-------|
+| `templates/base.html` | ⏳ Pending | Title, navigation, flash messages |
+| `templates/index.html` | ⏳ Pending | Section headers, table headers, messages |
+| `templates/add_tablet.html` | ⏳ Pending | Form labels, button |
+| `templates/add_user.html` | ⏳ Pending | Form labels, button |
+| `templates/loan_tablet.html` | ⏳ Pending | Form labels, button, search placeholders |
+| `templates/history.html` | ⏳ Pending | Section header, table headers, messages |
+| `templates/user_loans.html` | ⏳ Pending | All text content, search placeholder |
+| `templates/non_loanable_devices.html` | ⏳ Pending | Section header, table headers, messages, button |
+| `templates/edit_non_loanable_device.html` | ⏳ Pending | Form labels, buttons |
+| `templates/project_management.html` | ⏳ Pending | All text content, buttons |
+
+### Approach Options
+
+#### Option 1: Direct Template Translation (Recommended for simplicity)
+- Replace all English text with Spanish directly in templates
+- **Pros:** Simple, fast, no dependencies
+- **Cons:** Harder to maintain bilingual support
+
+#### Option 2: Flask-Babel Integration (Recommended for future i18n)
+```python
+# Install: pip install flask-babel
+from flask_babel import Babel, gettext as _
+
+app = Flask(__name__)
+babel = Babel(app)
+
+# In templates:
+# Before: <h1>Tablet Management System</h1>
+# After:  <h1>{{ _('Tablet Management System') }}</h1>
+```
+- **Pros:** Supports multiple languages, professional i18n
+- **Cons:** More complex setup, requires extracting strings
+
+#### Option 3: Jinja2 Macros
+```html
+{# macros.html #}
+{% macro trans(text) %}{{ text|trans }}{% endmacro %}
+
+{# In templates #}
+{% import 'macros.html' as m %}
+<h1>{{ m.trans('Tablet Management System') }}</h1>
+```
+- **Pros:** Reusable, clean templates
+- **Cons:** Requires macro setup
+
+### Recommended Spanish Translations
+
+| English | Spanish |
+|---------|---------|
+| Tablet Management System | Sistema de Gestión de Tablets |
+| Available Tablets | Tablets Disponibles |
+| Active Loans | Préstamos Activos |
+| Loan History | Historial de Préstamos |
+| User Loans | Préstamos por Usuario |
+| Non-Loanable Devices | Dispositivos No Prestables |
+| Project Management | Gestión de Proyectos |
+| Add Tablet | Añadir Tablet |
+| Add User | Añadir Usuario |
+| Loan Tablet | Prestar Tablet |
+| Return | Devolver |
+| Brand | Marca |
+| Model | Modelo |
+| Serial Number | Número de Serie |
+| Notes | Notas |
+| Name | Nombre |
+| Email | Correo Electrónico |
+| Phone | Teléfono |
+| Identification | Identificación |
+| Loan Date | Fecha de Préstamo |
+| Return Date | Fecha de Devolución |
+| Status | Estado |
+| Actions | Acciones |
+| Edit | Editar |
+| Delete | Eliminar |
+| Save | Guardar |
+| Search | Buscar |
+| No available tablets. | No hay tablets disponibles. |
+| No active loans. | No hay préstamos activos. |
+| No loan history available. | No hay historial de préstamos disponible. |
+
+### Implementation Notes
+- **Do not change code yet** - This is documentation only for now
+- Consider using a translation dictionary or Flask-Babel for maintainability
+- Test all translated text fits within the responsive design
+- Verify character encoding supports Spanish (UTF-8 should be fine)
+
+---
+
 ## Changes Made
 
 ### Date