If you want to build serious long-term wealth, these mid-cap Canadian stocks could be the slow and steady winners you’ve been looking for. You know that old saying, “Slow and steady wins the race?” That’s exactly how I’m thinking about mid-cap stocks right now. While most investors are distracted by short-term noise, it could be a smart move for Foolish investors to buy some solid Canadian mid-cap stocks now and hold for years to let them grow. Stick with me as I break down four top mid-cap stocks I’d be happy to buy today and forget about for the next 20, 30, or even 40 years. IAMGOLD stock First on the list is IAMGOLD (TSX:IMG) — a Toronto-headquartered gold mining stock that has rallied over 90% in the last year. The company mainly focuses on developing and operating gold mines across North America and West Africa. IMG stock is currently trading at $9.96 per share with a market cap of $5.7 billion. Last year, IAMGOLD’s revenue jumped as new production from the Côté Gold Mine kicked in. Similarly, its net profit surged due to higher gold prices and a major turnaround at Westwood mine. Bringing even more optimism, the company is advancing efforts to maximize Côté Gold’s output and grow its reserves, putting it on a path for long-term, stable growth. Innergex Renewable Energy stock Another mid-cap stock that fits perfectly into this “buy and hold for a generation” list is Innergex Renewable Energy (TSX:INE). It’s a top Canadian renewable energy producer that operates hydro, wind, solar, and battery storage facilities across Canada, the U.S., France, and Chile. INE stock is currently trading around $13.61 per share with a market cap of about $2.8 billion, and it offers a decent 2.6% annualized dividend yield. In the quarter ended December 2024, Innergex reported a 13% YoY jump in adjusted EBITDA (earnings before interest, taxes, depreciation, and amortization), supported by stronger wind and solar production and smart project additions like the Boswell Springs wind farm. Moreover, Innergex’s consistently expanding project pipeline and self-funded growth strategy clearly show why this Canadian stock could power portfolios for decades. Maple Leaf Foods stock Moving along, another Canadian mid-cap stock I’d like to highlight is Maple Leaf Foods (TSX:MFI). This food company is best known for its prepared meats, plant protein, and poultry products. MFI stock is currently trading at $24.84 per share with a market cap of around $3.1 billion, and it offers a decent annualized dividend yield of about 3.9%. In recent quarters, Maple Leaf Foods has been picking up the pace. Its fourth-quarter sales rose 4.3% YoY to $1.24 billion due to higher volumes in prepared meats and stronger pork market conditions. Meanwhile, its adjusted EBITDA jumped 29% YoY to $155 million as the company started seeing the full benefits of its new London poultry facility and Bacon Centre of Excellence. With a clear goal to maintain mid-single-digit sales growth despite economic uncertainties, MFI stock looks ready to keep delivering steady gains. Definity Financial stock Another mid-cap stock that deserves a spot on this list is Definity Financial (TSX:DFY). This top Canadian provider of property and casualty insurance offers products through brands like Economical Insurance and Sonnet. Currently, DFY stock trades around $39.20 per share with a market cap of roughly $4.6 billion. In the December 2024 quarter, Definity posted a 12.5% YoY rise in net premiums earned with the help of stronger pricing and solid retention across its key insurance segments. Similarly, its underwriting income improved with better claims management. With its continued investments in digital distribution, expanding broker networks, and focus on profitability, Definity has the potential to deliver compounding growth for years to come.