diff --git a/app/models/workout.py b/app/models/workout.py
index e69de29..9dc5403 100644
--- a/app/models/workout.py
+++ b/app/models/workout.py
@@ -0,0 +1,65 @@
+from . import db
+from datetime import datetime, date
+
+class User(db.Model):
+    __tablename__ = 'users'
+
+    id = db.Column(db.Integer, primary_key=True)
+    username = db.Column(db.String(80), unique=True, nullable=False)
+    email = db.Column(db.String(120), unique=True, nullable=True)
+    password_hash = db.Column(db.String(128), nullable=False)
+    profile_image_url = db.Column(db.String(255), nullable=True)
+    bio = db.Column(db.Text, nullable=True)
+    created_at = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
+    updated_at = db.Column(db.DateTime, nullable=False, default=datetime.utcnow, onupdate=datetime.utcnow)
+
+    workouts = db.relationship('Workout', backref='user', lazy=True, cascade="all, delete-orphan")
+
+    def __repr__(self):
+        return f'<User {self.username}>'
+
+class Workout(db.Model):
+    __tablename__ = 'workouts'
+
+    id = db.Column(db.Integer, primary_key=True)
+    user_id = db.Column(db.Integer, db.ForeignKey('users.id'), nullable=False)
+    title = db.Column(db.String(120), nullable=False)
+    workout_date = db.Column(db.Date, nullable=False, default=date.today)
+    memo = db.Column(db.Text, nullable=True)
+    created_at = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
+    updated_at = db.Column(db.DateTime, nullable=False, default=datetime.utcnow, onupdate=datetime.utcnow)
+
+    logs = db.relationship('WorkoutLog', backref='workout', lazy=True, cascade="all, delete-orphan")
+
+    def __repr__(self):
+        return f'<Workout {self.title} on {self.workout_date}>'
+
+class Exercise(db.Model):
+    __tablename__ = 'exercises'
+
+    id = db.Column(db.Integer, primary_key=True)
+    name = db.Column(db.String(120), unique=True, nullable=False)
+    target_muscle_group = db.Column(db.String(80), nullable=True)
+    description = db.Column(db.Text, nullable=True)
+    image_url = db.Column(db.String(255), nullable=True)
+
+    logs = db.relationship('WorkoutLog', backref='exercise', lazy=True)
+
+    def __repr__(self):
+        return f'<Exercise {self.name}>'
+
+class WorkoutLog(db.Model):
+    __tablename__ = 'workout_logs'
+
+    id = db.Column(db.Integer, primary_key=True)
+    workout_id = db.Column(db.Integer, db.ForeignKey('workouts.id'), nullable=False)
+    exercise_id = db.Column(db.Integer, db.ForeignKey('exercises.id'), nullable=False)
+    set_number = db.Column(db.Integer, nullable=False)
+    weight = db.Column(db.Float, nullable=False)
+    reps = db.Column(db.Integer, nullable=False)
+    unit = db.Column(db.String(10), nullable=False, default='kg')
+    created_at = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
+    updated_at = db.Column(db.DateTime, nullable=False, default=datetime.utcnow, onupdate=datetime.utcnow)
+
+    def __repr__(self):
+        return f'<Log: Set {self.set_number} of {self.exercise.name}>'
\ No newline at end of file